never used amazon to sell, but read the terms a while ago when considering it (didn't use Amazon marketplace because they charge 15% and other fees).
Anyways, iirc i thought if you categorize your item as a video game on Amazon marketplace, the standard shipping is $3.99; buyer buys your item pays Amazon, you ship item to buyer, amazon gives you the money for the item and $3.99 back less fees owed to them.
Not sure if there is a way around this, unless there is a loophole and sellers somehow select a higher shipping service method (priority, express, fed ex ground/ground, 2nd day air?) and tack on $7.99, but ship first class to rape on shipping fees.
Also, I recently updated the Pitney Bowes postage machine at my work for new fees effective April 17, 2011. Apparently, USPS is raising fees for first class mail. The one ounce rate will remain at $0.44, but additional ounces will increase. Not sure how much exactly (probably a few cents increase for each additional ounce), but i'm positive not enough to make shipping a game $8