Not sure if this is YMMV or not, but my Sam's had lots of Metal Gear Solid 4 discs for $52.99. Picked one up, as I didn't see it cheaper anywhere else.
my only issue with Sam's (and Costco) is, they don't always carry the game i want. it's hit or miss since i don't always go for the "popular" games.
but on another note you could get a better deal if you're willing to buy from buy.com and sign up for google checkout. buy.com has an instant $5 off... bringing it to 54.99... and new google checkout signups give $10 off... bringing it down to 44.99...
i'm not sure which route i'll take... still debating it...
I grabbed this on release day. Sam's has been very good at having the big name stuff on the day it comes out at a >10% discount. They're not reliable for everything up and down the pike, but for the big name stuff, the Nintendo first party stuff, and so on, they're a no-hassle way to get a good price and have it that day.