But personally I do not think it's too much at all. 20 mil is at max 1 hour trading with cargo ship of more than 4k cargo. That's pretty short time.
It is quite possible to finance upgrade from missions as well, including loot it's quite normal to get 1 mil per mission in Alpha, Gamma, Delta and similar systems. So that's 15 missions.
Gunboats now cost about 35 million, if you include at least normal upgrade and the necessary equipment (thruster, cm, cd) you are at some 55 mil. Then even normal turrets will cost you some 3 mil if you want razors/pulses/missiles it's much more. So let's say 60 mil.
60 mil is a lot more than 20 for a fighter. 60 mil for a ship that any fighter/bomber can simply thrust from. Again don't see any problem in prices.
Igiss says: Martin, you give them a finger, they bite off your arm.