I think I understand your point now, but then it is more about game balance than economy I would say. And making different strategies viable. If building a tank takes a lot of resources, then it is no problem if it is very good - the rest of the party will be weaker, but that doesn't matter. You have probably analysed the numbers a lot deeper than me, so I believe you if you say it needs tweaking.
In the end more extreme game plans / strategies should be harder to accomplish then more basic, mixed strategies. But if it is possible and good enough to beat the game, then I see no problem.
