Looking at the Chicago Conventions Calendar, the Plastics show is June 19-23 with 75,000 attendees estimated. That's one of the reasons why things are expensive for your dates. You are arriving on the 21st and departing on the 25th, for four nights of hotels, correct? Hotwire shows availability in NMA for all nights of your stay, 4* at $211. If you look at only 23-35, it drops to $191. Others may have a different opinion, but that indicates to me that hotels are aiming to get as many guests as possible above the Plastics convention rate. Here's a link to Plastics Show Convention Rates for hotels. You can't book them, but they could help frame your expectations. I think you could save a considerable amount of money splitting your bid. Ultimately the first two nights will be the issue. What do you think of splitting your bid? Are you familiar with the implications of that? Did you want to try for a hotel in the Loop for the final night, so you can be close to the car rental place?