Not sure which thread is still the active -- but to which 'track' do you refer? Indianapolis has three other venues in the area that if we wanted to run A/X or lapping, could be suitable. When he was still employed at IMS a few years ago, Joie Chitwood came to our local PCA banquet and I asked him about using the Speedway for something aside Indy 500, NASCAR, and/or F1. I was more referring to ALMS or other race series, but the topic of HPDE was broached. He went into depth about the costs. If anyone remembers F1 here, there was a "Ferrari Challenge" support race where privateers paid $$$$$$$$$ to run their own cars in a "race" on the F1 circuit. That is the kind of money that would be needed, he said, to even get IMS to think about thinking about considering the possibility of perhaps mentioning the thought of might there be a chance that the circuit could be made available. Now they are perfectly happen to cordon off an area of the Museum parking lot for a special paddock if arranged for ahead of time. But not for access to the track surface.
However, I did mention other possible venues. Just to the west of Indy is O'reily Raceway Park and it has a road course. Local PCA used to run club races here until we moved it to
Putnam Park (incidentally, we have our spring HPDE there this coming weekend! Spaces are still open!) which is about 40 miles west of Indianapolis. On the eastside is
Newcastle Raceway which is primarly for karting, but the local MINI club has run cars on their track before.
If lapping is desired, and Indy is the city of choice, I suggest picking a weekend that there is already a club hosting DE and pair up with them. Track rental for a weekend is around $22k at Putnam Park (weekdays are less, but I don't know specifics). That includes some insurance, corner workers, sanitation, crewed ambulance, etc. I don't know what ORP or Newcastle cost (but if there is interest I'll happily make a few calls).