They also cared about the PR issues of wiping out villages. They were there to "Liberate" not to wipe out.

You are correct it does make it cheaper (maybe, eventually), but so do bombs or gunships or drones.

These are hella complex machines though. A gun is absurdly simpler as is a drone. And the ground is a lot messier than the air.

The logistics of servicing/repairing them is also going to be hefty. Tanks are a pain for maintenance already and they are much less complicated.