Its a business decision by Xray.
Either they can sell the current kit @ $31xx.
or
Sell the current kit + metal shocks @ $38xx (just an estimate). but if they choose this way, they will scare off a lot of potential customers.
Never look down on the plastic shocks from Xray. They are even better than many metallic ones of other brands, especially for the adjustable pistons.....
XRAY plastic shock is very light-weighted and consistent in performance. If you look at XRAY Team drivers, nearly all of them are using the plastic shocks set. The reason probably be that the plastic shocks set is relatively easiler to adjust the rebounce in terms of time and effort required.