The Turning Stone event runs twice each year, in January and in August. Both are free to attend. That includes free parking in the casino lot and free admittance to the event center where the tables are set up for play.
I've been to Turning Stone for the 9-Ball event before, but only as a day trip. The way the tables are set up makes for very good viewing. Between rounds there are players practicing on the tables and most seemed willing to talk and take pictures with people, which was nice.
Have also stayed when a friend's band played at the Tin Rooster club there. The Turning Stone itself is a casino/hotel complex with a few golf courses, a half dozen or so nightclubs, and a handful of restaurants. They also own properties in the area, so some rooms that they list are not actually "on-site" for the casino. I've stayed at a place about 3 miles down the road and it was considered part of the Turning Stone, although much cheaper. There are shuttles that will take you back and forth, but I drove since I didn't want to be on their schedule. If you don't mind being 30 minutes away, I'm sure you can find a number of very nice and inexpensive places to stay.
Restaurants on-site are good, the steakhouse on the top floor was really nice but pricey, and nightlife covers almost every genre of music every weekend.
So to end the long winded reply, you can spend nothing at all if you make it a day trip, or you can spend a ton if you're on-site, gambling, and doing all the other stuff they offer.