You seem to not understand basic engineering. If the gas piston modifications were cheaper than the standard gas impingement tube, then you would be claiming that it's a superior system. AR15 fans don't want to hear that there may be anything wrong with the design of the system.
https://www.ar15.com/forums/ar-15/High_round_count_AR_M4_s__over_100_000_rounds__and_how_they_have_handled_on_our_range/118-677135/
https://defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/