It's a lot cheaper than the headline figures suggest. Also there is a lot of hope that future defense procurements are more cost-effective than in the past because the military is very conscious of how American "cost-disease" puts us at disadvantage to other nations and if we lose the next war we'll be probably be defeated by own defense contractors than the enemy.
While US soldiers aren't maneuvering here, we certainly are seeing how our equipment gets used as well as their weaknesses in practice. Chances are that when this is all done, Ukrainian commanders will participate in wargames to help share what they've learned with us as well.
It's best to keep an eye on the next war if at all possible. Ukraine very well is just a test run of what could happen in China vs Taiwan, and it's good to exercise USAs industrial might for this practice run.