Take in consideration that the samsung drives are 10 and 20 gb more then amd counterparts. AMD may be cheaper only by a couple bucks and they have a slower write speed.
The 10-20GB isn't worth that extra bit of money (10GB for $10). Also since these just came out prices are probably a tad higher than they'll end up. The R3's are a tad slower than the Samsungs while the R7's are a tad faster (and cheaper at 480/500GB). The R7's it looks like are OCZ/Toshiba drives.
If you're actually wanting the cheapest drive you can then a lot of other options linked above are a better choice. Assuming longevity is good on these drives I'd probably opt for an R7 480GB over the 850 500GB simply due to being cheaper, slightly faster, and branding.
I don't expect these to gain significant market share but they're priced and spec'd competitively. For me I'd get it simply because it's just as good as other options and has branding to match the rest of my part preferences.
