I've been on tons of retreats ranging in price from $140-$500. Most of them are Thurs-Sun.
Some don't have classes, some are very structured. You bring your food to some, others have all meals prepared for you.
The $500 one is in a very nice hotel with a well known restaurant that makes excellent food. It's put on by a quilt shop and they bring items to vend. They also do some raffles and games and will teach one class if you want to learn that project. The sewing room is huge and you can easily lay out a king size quilt on the floor with all 40 of us working in the same room. This is a really nice retreat, but expensive.
I'm going on one this fall for $140 from Thurs-Sun. They provide breakfast, we're on our own for the other meals. Many of us bring crock pots for dinner meals or go out to eat. We quilters bring so much food to share with everyone, that you can easily graze the goodie table for "lunch".
Another one I really like is in a Catholic Retreat house. That one is $300 from Thurs-Sun. We each have our own sleeping rooms with a full bathroom and a nice room for us all to sew in. They cook all our meals. The workers there (including the priests) love to come see what we're working on.
Retreats are awesome!