A lot more goes into an integrated system like this than just selecting a rifle, scope, suppressor, etc., and stuffing them into a transit (hard) case. Take the M110 SASS (Semi-Automatic Sniper System), which I notice this new rifle is NOT replacing. In addition to all the pre-contract admin work, you get the rifle, scope, mount, suppressor, bipod, sling, numerous magazines, three different cleaning kits (I dunno why three), repair parts, special tools, a soft case/drag bag, and probably some additional stuff that I've forgotten about, all in a really cool and durable hard transit case. Cost? About $13K, last I checked. Also included in that price is technical support and training by the manufacturer (Knight's Armament). Could one assemble a comparable (but not identical) kit by piecing it together, for less money? Doubtless, if you wanted to expend the time and hassle of dealing with a dozen different manufacturers/vendors.
On a related note, I wonder what Uncle is gonna do with all those surplus M2010s, M40A5s and 6s, etc.? I know they would never, ever consider surplusing and selling off M107s (except maybe to LEAs in Cali, to whom Barrett will not sell).