Summer prices. Bummer. Have you tried using Priceline?
Is there a specific reason to staying in BUF? Airport? If your finding BUF so expensive, why not stay a bit further out (not sure where coming from and why over there) but try Fort Erie?
Comfort Inn and HoJo usually pretty good?
Comfort Inn for the 27th is $100 and HoJo is $95.
Not sure if these are options but not bad prices??
If you DO need the airport, it is only 15 min over the border.
I think with the dollar being so good, lots of people are doing back to school shopping in the US, and filling the BUF hotels. We just got back from a last minute overnight trip to Buffalo, and we had a hard time getting a hotel at the last minute. All of the Marriott family of hotels were fully booked up, even for Marriott rewards members, so there's no way that one of their hotels would have been available through Priceline.
Have you tried the Sleep Inn or the Comfort Suites? They're usually pretty reasonable and they should have rooms that accommodate 5.
That's the problem you will run into if you want to be right on site. The amount of time it takes(which is very little) to drive from a bit further out, is well worth the money saving and time wise it will honestly make no difference at all. I can try to also do a search to see if I can find anything. You can pm me.
My guess would be that it's the Saturday night going into the last week of the summer and with a long weekend following. Lots of travelers.