Well, if we would judge 5 or 10 period we could make some conclusions. IMO:
USA stands as one of the most overpaid NT. Their budget would beat any possible NT in huge difference, but they weren't that dominating in international tournaments this decade.
I believe France could pretend as the second most overpaid NT this decade. Parker, Diaw (NBA stars) and plenty of other NBA players mean very solid contracts and they were very unstable this decade in BB courts.
Lithuania, Greece, I think would stand somewhere in the middle. Lithuania could be one of the best NT here while some of our key players are underrated IMO (Šiška's contract is funny compering to his contribution, Kaukėnas was somehow unknown for big clubs for the long time), but lately some Lithuanian players hit some records (Šaras, Kleiza. Guess in which country they play

) Greece players have solid contracts while their players are playing in PAO/OLY mostly.
Spain and Argentina IMO is very adequate in the salaries and sport results. Very stable in both ends I guess
Italy comes as the most efficient NT this decade. Without superstars (arguably) they managed to be very tough in every tournament till 2006 I guess.