But as the technology gets cheaper and mass production kicks in a CD is less than 50c worth of plastic and the music is a printed label with the music printed on the underside of the label.
The first AESA modules will be hundreds or even thousands of dollars each, but when aircraft and vehicles and ships and SAM radars and even missiles and satellites get AESA radars the number of modules you make a year becomes billions or trillions... a new R-77 ARH missile has 64 modules each... the enormous 2,500km range radar of the S-500 probably has hundreds of thousands of modules each... ship radars will be enormous too... Armata tanks use AESA radars to detect incoming threats, and UAVs will carry radars too.
As production continues they will make them faster and more accurately with fewer duds and the production price will go down to dollars or even cents per module...
They could even use them in motor vehicles for collision prevention and parking to improve on the current sensors used for those jobs.
If the choice is to keep a MiG-21 with operational costs of maybe $4,000 per flight hour and put a $1,500,000 dollar new AESA radar in its nose, or have to buy a new $35 million dollar MiG-29 or F-16 with a 1.5 million dollar radar in their noses, but pay $15,000 per flight hour... and also buy all new parts and retrain your ground crews and pilots.
The reality is that the vast majority of countries with an air force don't really need fighters, and generally the fighters they have they really don't need anyway.
I mean WTF does Germany actually do with its fighter planes?
If you gave Poland F-35s... how long would they last in real combat?
More importantly... how many hours would they be able to afford to keep them operational?