Play the game and see for yourself... Vehicles that perform well enough to unbalance gameplay have a cost.
The cost is determined by ENY values, which you can see in the hangar.. these ENY values equate how many perk points you get for a shooting down a given vehicle in a specific vehicle. OBJ values are used to number how many points you get for destroying objects (Hangars, Ships, AAA, etc.)
Perk points are the currency for that "cost".. hence 'perked' vehicles.
You then get the total points earned in a sortie multiplied by either 1 for dying, ditching, or bailing, 1.25 for landing, and 1.5 for landing on a CV.
And lastly, there is a perk multiplier for each country, that varies inversely with the population of the country relative to the others'.