My favorite shop recently had a free 'open quilting' on a Saturday just to give us some air conditioning and company. There were some pastries and a coffee pot and it was from 10-3PM! And there was a discount on anything we purchased that day if we had signed up for the open day. It was great! And she sold a lot of merchandise.
Another shop I like charges for the 'open classes' at $40 for 2 hour sessions, but there is an instructor who can help you with your projects; you are supposed to buy the material from their store for your project. It's a lot of fun and we all learn something.
I don't think you can object to paying for use of the store workspace. It's sure more convenient than getting 12 people gathered around my kitchen table, or crammed into my sewing room, blowing fuses left and right, fighting over the ironing board, wondering what happened to the Best Press, complaining about the lack of A/C...LOL -