There's no way to guess at the cost, but it won't be cheap, frame pullers are very slow so it takes a lot of time, and time is money. If the damage isn't too severe it can be fixed close to new condition, but you'll have to talk to a good frame shop to find out for sure. It sounds like your damage is more toward the severe range so I would guess its gonna be costly if it can be fixed right. Keep in mind, no matter what a shop tells you, that due to the nature of metals, once a frame is bent it will never be as strong again no matter how expertly fixed, and it is very hard to get it right in all 3 dimensions.
The artist formerly known as SteedaMatt.