Nicely done!
It seems that CO may have come to its senses with respect to bump compensation. In the past, I have seen them IDB people, pay them $400 in CASH, then endorse their ticket to Delta (more cash out) because they refused to up the ante from the usual $300. This, by the way, was when they had adequate potential volunteers who said they would take $400 or $500 in voucher.
You did take a risk, though. If there were other takers, your $500 request would definitely have been denied.