It's a three word doman. there is already OilPrices.com and GasPrices.com
ask yourself why would someone want GulfOilPrices in king if there are those two above? Shorter is better. This is why three word domains are "problematic".
Mike Mann say's stick to two word domains. it's the smart way to go.
of course there are exceptions to the rule.
so ask yourself. is your domain THEE EXCEPTION?
I'd counter the middle $xxx offer with triple the price and have a goal to get somewhere in the middle.
Sell and move on.
It's all about as Generic as possible.
OilPrices.com is generic enough to cover oil from all over the world not just the Gulf.