Not sure, I'd say the budget was likely comparable to other AAA titles of the time but really, it was one of the first games i am aware of that really focused on realism as opposed to an arcadey experience. Movement in the game was slow and intentional, you had to use smoke to cover your movement, lean around corners, use suppresive fire, it had a mechanic that blurred vision when being shot at... It was one of the first to use iron sights and limit how many players could select classes like marksman per squad. You had a fixed number of magazines and reloading a partially empty magazine didn't just magically fill it back up, you ended up with a half empty magazine haha... Literally never saw this again until Tarkov came out.

We take all this stuff for granted now but they did all this in 2002, nobody but them at the time pulled all of this into a single game.

The closest game experience to America's Army I'd say was the Red Orchestra series.

Now there's lots trying to do what they did, at a bigger scale, games like Hell Let Loose, Squad, Insurgency, Rising Storm, Post Scriptum in my opinion all owe themselves and are part of the groundwork and lineage set by America's Army... Hell even the pacing and controls of PuBG are reminiscent