Haker Dojo charges a $100/month.
As does TechShop (approximately), for "membership." Which is not the same thing as requiring that you be a member in order to attend a workshop that might be presented there. (not that it means there ARE any such workshops 
)
I dunno. Designing a "workshop" is HARD. Especially given the wide range of user expertise that such a workshop is likely to have show up...