GP goes for roughly $0.45-$0.60/M depending on who you sell to, so whatever the street price is just multiply it by the amount of $/M you're looking for.
I plan on buying one soon, as I've recently received a BAD ASS job interview... and should have a job soon. So, with current inflation rates, I can expect to pay $700 in a few months, when I can purchase it. Just going with a strait .50c price, ofc. MM'd, as well. The issue for you wont be selling your phat- people will be interested in buying it- the issue will be finding someone who won't charge back.