I have about 1000 sq feet. I started in a small bedroom next to the kitchen, then we added on 3 times. (YAY!) I have a 12 ft. longarm, a 2 head commercial embroidery machine, a 10 1/2 x 3 1/2 ft cutting table, 3 sewing machines, 1 Sashiko machine, a seger, filing cabinet, computer and printer, small table and chairs and a smaller cutting table. I still wish I had more room. LOL
I think it goes - however much room you have want more. I sew or quilt everyday so the space is really used. I love it!
My DH likes to tease me about how much room I have, but then I point out how large his barns are.