I just signed up for my first classes at the guild I just joined (so I'm a total newbie at all of this) - the classes I signed up for were paid for in full up front; $40 per class and then one class will have $15 kits you'll need to buy from the instructor during class. (One is taught by a guild member, the other is taught by a "big name") I think they ask for 48 hours notice if you're not going to make it, in order to get your $40 back. That seems completely reasonable to me.
The price is maybe a little steep (seemed especially expensive when paying for 2 classes at once) and I'm sure some guild members are priced out of classes, though. I'm not sure if there's any program in place to help lower income guild members be able to attend...I hope there is.