None of the door kits I've seen are really cheap. whatever you get make sure they are true Lambo style- straight up....none of that droop to the side and hard to get into stuff.
ive seen them as low as 500.00 but you might get some flames if you do them. The only thing i dont like is they are never TRUE lambo doors because they are not made for that kinda door. They usually pop out and then up instead of going straight up. Anywayz if thats what you look to each his own and i think thats all that matters. good luck