I was wondering I always hear people saying i got my truck for like 15,000 off the sticker. How do they do that? And whats this GM supplier discount?

If you can find a dealer who is willing to sell below invoice plus loyalty rebate (1500), regular rebate (2000), GM card (up to 2500) and the military (500), that is over $13,000 off MRSP of a loaded dmax