To shed a little light on the "shitty deathcore bands on legit metal shows" discussion. Based on my ~5 years experience doing shows in my own band, this is how it works:
If a headlining band wants a $5,000 guarantee, rather than actually do any work to promote the show, or at least test the market for interest to see that the headliners are even capable of drawing enough to make sure the show won't bomb, the promoters will let 5 local bands buy onto the show, prebuying 50 tickets at $20 apiece ($1,000 apiece, so 5 grand total). That way, no matter what happens, the show won't bomb and everyone will make their money.
That being said, it's been my experience that 80% of bands don't even come close to selling the tickets they prebuy, the just get burned and look at it as "paying to play", which is why the shows are still half-empty even though the openers had to pre-buy 250 tickets.