You're calling $150 to win $490. You're getting about 3.2:1 on your money. If he's got the nuts, you're a 4.5:1 'dog. If he's drawing to the flush with an overpair, you're a 4.5:1 favourite. Which seems more likely to you?

Btw, I'm an amateur, take this with a pinch of salt, but I think this is the right way to think.