Ideally I would cut the cost for armor by 1/2.
Then I would multiply the cost of structure by about 50.
This way my average cost of structure damage would be about 20-40,000 C-Bills on mech loss, and the cost of armor would be 10-50,000 depending on the mech I am piloting. Thus the total cost of repair would be about the same, so you whiny kids dont cry, and it makes a hell of a lot more sense. You would then modify these numbers based on the Ferro and Endo upgrades of course.
EDIT:
Endo-Steel needs to be very expensive to fix. Because currently Endo-Steel is very cheap for repairs and there is no reason why you shouldn't get it. There needs to be a counter argument or a balance between upgraded and un-upgraded mechs. In this case the balance would be that Endo mechs are lighter and easier to fit, but unupgraded structure is much cheaper to use.
Edited by RogueRAZR, 01 November 2012 - 01:05 PM.