Oi.... 300 million for a gunboat! That's.... INSANITY! I'm not spending a week and a half trading to get a 6 turret thing. My problem with insanity prices are I use my ships for RP purposes. RM in Rheinland ships. I plan on having one of each. Battleship, Cruiser, Gunboat, Fighter, Bomber. I'm missing the expensive ones. Why? They cost a lot of money. That price, only people ALREADY WITH battleships will ever have them. No one will spend that much time to get one.
I think your idea could be OK. But not the prices your suggesting...