There is a lack of inventory on this rifle and also the MR556, there is one mr762 on gunbroker for sale.
The LR version hasn't been available for over a year.
It's nice to have, but honestly not worth the premium.
I'm with others you're better off with JP, Gap, Larue, for DI.
If you really want a piston gun it may make sense to look at LWRC CSSAS.