I have a hard time believing the 550-1. An after-the-fact google search brings up vegasinsider.com showing that, but doesn't say which book was offering it. Even if those are the implied odds based on the point spread (props to the Wizard for being the best source: https://wizardofodds.com/games/sports-betting/appendix/11/ (everyone else stops at +20)), no Las Vegas book would ever expose themselves to that sort of liability. Can't think of any reputable online books would either. We can check the 35+ point spreads in the upcoming weeks and see if anyone really does have moneylines on those games
It wasn't long ago I seen some soccer team was a 5000 to 1 shot and I thought some European Casinos booked that action. I could be mixed up though and completely wrong.
I doubt the odds were ~500:1. That implies about 0.2% chance to win. Take out the juice and it's probably 0.05-0.1% chance to win.
I'd probably take those odds, even if it was some sh** college team vs the patriots.