I'm not sure, but the reason why someone may be skeptical is because you bumped your own thread with the word "legit" - and your grammar isn't the best "why wouldn't be this a deal?". These are usually two signs of shady business - or maybe that's just me. Who knows.
For the record though, this is compatible and is a legitimate deal. I've purchase four 4gb kits from fry's now, and this is definitely the lowest price a 4gb kit has ever been. The deals been on for a few days now - it seems everybody's bought their share of 4gb kits already.