Radio Shack's $149 price for the 16GB iPhone 4 just got undercut by a whole two bucks. We've been tipped off to Sam's Club now offering the AT&T-locked device for a $147 fee, subject to the usual two-year agreement. This offer will run all the way until Christmas day, so if you have to have the cheapest possible fourth-gen iPhone, this'll probably be it. The 3GS is also up for grabs at a thrifty $47, emulating its younger sibling's $52 price cut. Is there anyone left who isn'tdiscounting smartphones this month?