Pricing should increase for the frames, cloth tarp, timber, and brick slabs starting in T3 as each one requires the resources PLUS additional T2 resources to craft. Having the price the same leads to a loss for the crafters in economies that are based on task prices, like in New Haven.
I know the price is 1 to 1 Hexcoins to Supply ratio, so maybe drop the reward from hand in in just 10 ingots, in this case, a reward of 750 for 20 T3 ingots would cover the cost of the resources required to make T3 Frames.