Why is it in the game at all? I, for one, certainly haven't noticed the effect. I fly for the team with the least numbers, but that is just general principle for me. Usually its still the rooks, but sometimes its the bish or knights.
And personally speaking, I don't see any effect at all. Typically numbers aren't to lopsided until reset is imminant (say 5 bases or so), but two teams sides will typically wear down the other side until the third side is down to 5 bases and people start logging off. Then one of the two goes for the reset, while half the other team continues fighting the third team and the other half try to pull out the reset by attacking the top team. By the time the numbers get low enough that a 262 is "affordable" (and to be honest, I don't know that it ever truly is, with 99% of the "newbies" in planes with ENY's of 10), the maps all but reset.
So I guess my suggestion would be to tie in base numbers as well, and give them an effect. So that way if a side has 10 bases and only 20 fewer people than their alloted "33%" of the population, they'll still see somewhat of a price break until the field numbers even up again. Of course, this is all but a moot point, since nobody flies the perk planes anyway. Which I suppose is just the way you want it, or you'd have set the system up differently.