The MR556 is being made in the states so as to be allowed for civilian sales. A guy over at ar15.com saw one on display at a recent gunshow, and word is that more will become available shortly.
The MSRP is around $3k. I guess that means that lunatics on both sides of the dealing table will make it sell for that much at first, but like the SCAR, prices will settle with time.
If HK didn't care about civilian sales, you wouldn't see ANY of their products available to you, period. We must remember that the reason the classic roller-locked guns are not available is the import ban from Bush Sr. (people tend to forget that Republicans ban stuff too).
Honestly, the MR556 really is a day late and a dollar short. There was a period of time where piston ARs held all the attention of the gun-savvy populace, but now their attention is focused on completely new designs using piston technology. I had a chance to hold a prototype MR556 and that thing was just too heavy. I think these new HK offerings will be a big letdown for most people. A lot of people just want what they see in magazines, the net, or on tv. Once they actually get their hands on 'em, they're underwhelmed. I am pretty confident that this will be the case with the "Mister" series.