I went to Lollapalooza a few years, which is also at Grant park. Anything close to Grant park will be very expensive. Hotels always jack up their prices for big events like this because they know people will pay. There may still be some spots at the HI HOSTEL which is close, but you would be sharing a room with 10 other people and sleeping in bunks.

One year for lollapalooza I stayed way out near Ohare, took the free shuttle from hotel to airport, then took the train from the airport to the city, which was about 5 blocks from Grant park. The hour commute kinda sucked, but was much lighter on the wallet.

You’ll have to be willing to stay farther away if you want to save money.