Amazon made waves back in February when they dropped the price of the Motorola Atrix 4G smartphone on their site to $129.99 (with purchase of a new AT&T plan).

Now they have dropped the price again – to $49.99 (with purchase of a new AT&T plan). This compares to a price of $199 (with new plan purchase) at AT&T stores. Amazon is also offering a promotional code with the Atrix that is good for $100 off an AT&T laptop dock.

The price drop and undercutting of the AT&T in-store price of the Atrix comes on the heals of two other online AT&T discount resellers, Wirefly and LetsTalk, abruptly dropping their AT&T lineups just over a month ago. The later two regularly undercut AT&T’s (and other carriers) in-store pricing. It has been their main marketing strategy for years. No explanation for the break-up has been forthcoming from AT&T nor the resellers.

The Motorola Atrix 4G smartphone was introduced at CES 2011, where it won Best Of Show. It features a 4″ HD touchscreen, 5 mp camera, 3D graphics, a 2 chipset dual core processor, 1 gig of ram, 16 gig of internal memory, 4G speed, and it runs on an Android 2.2 OS. It weighs 4.76 ounces and measures 4.64″ by 2.5″ by 0.43″.

The laptop dock, which is retailed at $499, is on sale at Amazon right now for $399. With the $100 promo code that comes from Amazon with the Atrix purchase applied, it would $299. The Atrix slides into the laptop dock to provide a laptop like functionality. The dock has an 11.6″ screen, a laptop size keyboard, a touchpad, stereo speakers, and its own battery that will power it for up to 8 hours, according to AT&T.

Amazon’s wireless store is at wireless.amazon.com