What percentage of the budget was it? I think that's also needed for a meaningful comparison. I've heard about the war taxes being high, but I don't know anything about the economy of the time otherwise.
I wasn't actually comparing it in terms of dollars for dollars between the projects, more the national security aspect and the probability of the government pulling whatever levers are necessary to keep it going.
I didn't have budgets handy, but GDP is another way to normalise its cost to the country; ~$2.2B cost in 1942 with a nominal GDP of $166B, nominal GDP of $29.2T in 2024 puts the Manhattan Project's cost relative to GDP at $386B in 2024.
Nominal GDP from https://en.wikipedia.org/wiki/Economic_statistics_of_the_Uni...