KT isn't 260 fuel, your calculations are still wrong.
And last time I checked three OKW tiers cost more than 2 UKF tiers.
So it is. Had the old value in my head.
So the most expensive option is as much as the Croc/FF, the other three stand at cheaper.
I'm not including teching because the mix of tech tiers, sidegrades and optional unlocks make it a complex mess that deserves a thread of its own - but in general, works out fine and with similar total expense. The CP delay for the croc and builsing delay for the KT stack up and unless you float a lot and double down on inf AT neither is your first vehicle.
Regardless, the point was much, much simpler.
Croc + Firefly is good. Kf course it is. It's nearly 400 sodding fuel spent on vehicles. Any conbination of 400 fuel of vehicles is going to be a tour de force.