Hello!
It's not so much about taking so long before the surgery it's honestly about the doctor/staff making sure you have enough information about the surgery before actually doing it. They want to be sure that you know what you're getting yourself into. The office will also make sure you are in the right state of mind before being able to do the surgery (Psych Eval). You are also to meet with a Nutritionist as well so you know what kind of guidelines to follow after surgery. Most if not all doctors want to get clearance from the following: Family Doctor, GI, Cardiologist, Pulmonary and as mentioned the Nutritionist. The reason for those are to make sure you are not a high risk surgery, because the doctor doesn't want something to happen during or after surgery.
All things being considered it really isn't that long of a wait for surgery. You have to see all the doctors listed above and do all the test that they may order. As for payment/cost it's all about your insurance. If you have coverage for this kind of surgery is always a good thing, otherwise I believe in most cases it could cost upwards around $10,000. Not cheap, but could be very rewarding.