Don't you have a written confirmation of your reservation? Also, many of the MGM group of hotels charge an additional "resort fee" of $15-$20/per night--this still wouldn't have such a large discrepancy.
I have the e-mail they sent when I reserved the room.
I figure I'm screwed because I initialed and signed the room rates the receptionist put on the receipt. The only way I'm getting out of this is if they overcharged for the purpose of incidentals.
I mean, it's going on the taxes as a business expense. And it's my fault for not paying attention. But it's short of bill shock and a bad way to start my CES trip.