~ Reduction in Recoil

~ Improved Accuracy due to the reduction of recoil
I think they mean improved follow up shots? I also fail to see how reduced recoil increases the inherrant accuracy of the gun.

If recoil is reduced, would the recoil spring not need replaced to function reliably?

Retro-Fit Piston Driven System for AR-15/M-16

$499.95
Additionally the Retro-Fit System offered by Adams Arms will save Law Enforcement, Private Citizens, and other entities thousands of dollars by offering a simple upgrade option, instead of costly replacements.
Combined total yes, but if you figure that a bushy piston driven upper is $950 and you sell your old upper cheap at $300. That's a $150 savings over a known manufacturer.

~ Our Retro-Fit Piston Driven System has undergone extensive stress testing for reliability in the most extreme conditions
How many front sight/Tactical response classes have you run one through without failure? From everything i've been told, those are EXTREME conditions.