Thanks, JeffDime!
I've stayed at the Rio 3 or 4 times over the past few years for WSOP. The first time I got the Masquerade tower because I didn't know any better but then I always got the other tower ("Mountain View" when you're booking). I just checked and yes, Bally's is only a little more with Harrah's about even with Bally's. I was surprised to see Linq and Flamingo significantly higher.
Right now I can book 4 nights at Rio for $189 including the weekend.