I had the same feeling. That’s a rounding error in some of the recent things America has spent money on like the infra bill and CARES act.
The defense budget for 2022 in USA is $768 billion for just one year. The budget for the entire development of the telescope was 1.351351% of that budget.
Government budgets are well spent when they are used to do things that are impossible, unfeasible or unwise to do by individual people. JWST is a science investment, which is one of the wisest ways to spend public money.
Anyway I’m sure most Americans would’ve been happy with the 10 dollars a year or whatever it took over the time that 10 billion was spent