I kept this every year but fell off after 2015.  Decided to revive.  Here are most downtown hotels and how the prices increased.  Note the increase this year is over 2015 prices.  I used the lowest published price on the Gen Con site.  Looks like the forums don't handle HTML like they used to: 

Hotel    2019    Incr.    2015    Incr.    2014
Candlewood Suites Indianapolis Downtown    $190    8.57%    $175    2.94%    $170
Columbia Club    $207    9.52%    $189    2.72%    $184
Conrad Indianapolis    $259    10.68%    $234    2.63%    $228
Courtyard by Marriott Capitol    $204    10.27%    $185    3.35%    $179
Courtyard by Marriott Downtown    $212    7.61%    $197    3.14%    $191
Crowne Plaza at the Union Station    $220    10.00%    $200    3.09%    $194
Embassy Suites Downtown    $244    8.93%    $224    3.23%    $217
Fairfield Inn & Suites Indianapolis Downtown    $193    10.29%    $175    2.94%    $170
Hampton Inn Downtown    $211    13.44%    $186    3.33%    $180
Hilton Garden Inn Indianapolis Downtown    $216    10.20%    $196    3.16%    $190
Hilton Indianapolis    $200    19.76%    $167    3.09%    $162
Holiday Inn Express Hotel & Suites City Center    $205    10.22%    $186    3.33%    $180
Hyatt Regency Indianapolis    $234    10.38%    $212    2.91%    $206
JW Marriott Indianapolis    $246    12.84%    $218    2.83%    $212
Le Meridien Indianapolis    $245    11.36%    $220        
Marriott Indianapolis Downtown    $235    10.85%    $212        
Omni Severin    $222    10.45%    $201    3.08%    $195
Sheraton Indianapolis City Center    $213    10.36%    $193    2.66%    $188
SpringHill Suites    $204    10.27%    $185    2.78%    $180
Staybridge Suites Indianapolis City Centre    $210    7.14%    $196    8.89%    $180
The Alexander    $217    10.71%    $196        
The Westin    $221    9.95%    $201    3.08%    $195

Biggest increase over 2015:
Hilton Indianapolis    $200    19.76%   (2015 $167)

Smallest:
Staybridge Suites Indianapolis City Centre    $210    7.14%  (2015  $196)

Average:10.63%

Closest to average: 
Conrad Indianapolis    $259    10.68%    (2015 $234)

Hilton also "wins" for highest increase since 2013:
2013: $158  2019: $200  26.58%

Lowest since 2013:
Courtyard by Marriott Downtown
2013: $185  2019: $212  14.59%

And yet the Hilton stays as lowest priced downtown hotel.  Would love it if it was still only 158

With the hotel rooms increasing so much in the next few years, it will be interesting what prices do.  I would guess downtown demand for Gen Con will still outstrip supply and it doesn't look like any pressure is put on hotels to manage prices.  

I would expect though some lower prices outside of downtown. 

I am just wondering why you think there should be pressure on Hotels to "manage" their prices .
Just as in any convention city (or any location) when the demand for the rooms exceeds supply hotels raise their prices . The hotels are there to make money for their parent corporation and/or shareholders . Just the same as any business . Take the cost of food and beverage within the convention center and the stadium - you can find cheaper further away ,so you are paying for convenience-just like the downtown hotel rooms.
They also need to pay for the extra help brought in during the convention. 

Most of those prices are still inexpensive for a convention that uses such a high percentage of the rooms available.

Gen Con too is there to make money for its stakeholders.  There is really no excuse for higher than inflation hotel room increases.  It is supply and demand, and Gen Con is also in that equation so it can demand hotels have better rates, which frees up money for Gen Con badge increases and vendor purchases, as well as spending in the area. 

Unlike a a lot of convention areas, Indy (which is a tier 2 city) has the reputation of acting like a tier 1 city.  In other cities that can handle it, a similar sized convention could get lower rates. But Indy has to survive months of no convention business perhaps harsher than others. Still this higher than inflation gouging is having an impact. Look at the number of restaurants with prime locations that have folded, even as more hotels are built.

It is getting to a point where the only player for convention spend outside the con will be the hotels and the food trucks. 

The current hotel rate increases are untenable.  The hotels will fill, but people will spend less and less outside of their hotel bill. 

Not sure where you are getting your data, but inflation lately is 2% or lower. 

The CPI inflation rate since 2015 means that a $167 hotel room in 2015 should be $180 today.

The $158 2013 Hilton room should be $173 today if only due to inflation. 

I'm actually glad that the hotels have a chance to charge a bit more than inflation. They don't HAVE to be in the GenCon block. If they decided to just charge 'market rates' and be out of block, then GenCon attendees would be paying more overall. It's not unreasonable to give them a small increase each year, as incentive to go with the housing block. 

I also attend San Diego Comic Con, and downtown hotels are their number one issue. So many of them want to opt out of the block and charge 'market rates' of up to $1,000 per night, but heavy pressure from the Mayor and the convention center keep them in the block, although it feels like there are fewer and fewer rooms available there every year.

Let's not rock the boat at GenCon and allow the hotels small increases. 

Only problem is the boat looks to be taking on water as more and more local businesses around the convention center sit vacant.  Palimino, Scotty’s, Broken English/Tilted Kilt, Hard Rock, Noodles & Co. 

We are working towards an area with lots of hotels and nothing else.  Maybe only locals will notice. But it seems it may head towards a tipping point. 

I bet within the next decade we see one hotel at least shutter after making its short term profits and recouping building cost. 

I seriously doubt any of the closures  mentioned above were in any way related to Gencon hotel rates . If they is any actual evidence to show this I would be fascinated to read it .
Actual evidence ,not "I spoke to an employee..."
The closures listed above were due to a number of reasons from -Embezzlement , Bad corporate management , over expansion , lawsuits related to sexual harassment , owners getting tired , inadequate adjustment to trends  and a number of other reasons , including high downtown  tax rates .

They have been replaced by other stores and businesses . That is the nature of business .
Of course there will be hotel  closings ,and openings , again that is the nature of the business. It also is in the business plan of a number of Hotels (the smaller ones ).
Local business is much more important to the hotels long term viability than 1 week in August . When Hotels lose the Eli Lilly contract or the Anthem contract , that affects them.

Take a look at the downtown business map over the last 12 years -constant change in businesses . As in every single city . I have yet to see an article that blamed rising hotels costs for a restaurant closure .
The IBJ series of articles did a good job of discussing why - and explaining that Indianapolis'  rate was not any different than  any big city .

More likely that restaurant closings are affected by the increase of food trucks in the city than by hotel prices (not that the trucks are the only factor, of course). That happens in a lot of places too. Certain restaurants that aren't seen as standing out from the crowd don't hold up as well. (I'm honestly surprised that people still go to Hard Rock, fwiw. That seems like a thing that was dead a while ago.)

I'm sure there are some places, but applebees, hard rock, etc. level restuarants have a hard time surviving in downtown areas that aren't super touristy because people either want good food, or they want cheap food.  They don't want mediocre food at high prices.

Food trucks - stand in line for 20+ minutes only to be told "sorry we're sold out"  Go to a different truck and pay 12.99 for 3 oz of pulled chicken on a bun that was purchased at a grocery (and stale to boot) or better yet, pay the same price for a small piece of steak on a skewer that ended up making my daughter sick so she missed a whole day of the con last year.

If you remember the names of the trucks, please share them, as we should definitely not reward bad experiences with anonymity.   

For my own part, I have had good experiences with the food trucks.   I can definitely recommend Mac Genie, for instance.   Great portion size and extremely good Mac and Cheese.

Ali Baba was good the time that I went, but a little expensive for what you get.

There is a Venezuelan truck that was excellent as well.

Sadly, I don't know the names of more of the trucks that I ate from.   I am mobility impaired, so my brother does the truck runs and brings them back to the hotel (we've lucked out and gotten rooms at the Omni the last three years).