Why would they put phased arrays on UAVs? They are typically using beam-forming antennas + cheap gimbals for the same purpose.
Phased arrays are nice when you want to scan a large angular surface very fast; when it comes down to optimizing RF radiation toward your ground station, a gimbal is cheaper, simpler, and works fine.
Really depends; there you can see both Lockmart exhibiting multi-billions project, and 150m after some Serbian company selling jet engines for UAVs for a couple hundreds.
The first phased array systems date back to 1905.
We have had some time to productionize this.
Hell, the "PA" in "PATRIOT missile" stands for "Phased Array".