Ok, looking at your list.
P-51D = 8
F4U-A1 = 15
P47-D25 = 25
190-D9 = 15
109-K4 = 20
La-7 = 5
Of those 5 planes, which would you say is the easiest to learn to fly and get kills in, and be able to RTB?
My money would be on the La7, which puts it exactly where it should be, low.
Other end of the spectrum, you have the P47-D25 which is a much harder plane to go out and get those kills in and be able to RTB. Hence ENY of 25. Your going to earn perks 5 times faster in a P47-d25 as you will in an La7.
Why? Because its that much harder to do.
Personally I think the 109K4 is set too high, that thing is a monster.
So to rearrange your list in ENY order.
La-7 = 5
P-51D = 8
F4U-A1 = 15
190-D9 = 15
P47-D25 = 25
Would you really say that the 190D9 is as easy to fly and get kills in as the P51 or la7?
Or is the list stacked in terms of difficulty (and possibly partially popularity)