From a 2021 Government Accountability Office Report:
”According to data obtained from DOD, Japan provided $12.6 billion and South Korea provided $5.8 billion from 2016 through 2019 in cash payments and in-kind financial support. This direct financial support paid for certain costs, such as labor, construction, and utilities. In addition to direct financial support, Japan and South Korea provided indirect support, such as forgone rents on land and facilities used by U.S. forces, as well as waived taxes, according to DOD officials.”
https://www.gao.gov/product
These bases exist as a deterrent against NK and Chinese aggression and provide for the defense of those nations. Both NK and China are aggressors in the Pacific and Russia in Europe.
NK with threats to the U.S. and its allies, pursuit of nuclear capabilities, and intermittent rocket launches. The U.S. is still in a state of war with NK.
China continues to harass civilian vessels and claiming territory beyond the nine dash line. They present an ongoing concern of military invasion into Taiwan.
The U.S. receiving forms of compensation for supporting the defense of other nations is not a new thing. According to Zelenskyy the U.S. has provided $100 Billion in aid. Compensation on the back end would neither be a reparation or penalty.
I guarantee if Biden brokered a deal for Ukraine to compensate the U.S. post war, leftists would praise his efforts as a way of strengthening economic ties and mutual defense with an ally.