HotA - General Questions and Discussions

Yes, adding a gold cost for transformation (a fixed price for converting each unit of resource would be the most logical) would look good and add to the atmosphere.

With 9 markets, 1 valuable resource costs 1000 gold or 2 other valuable resources. You could then set it to 1 valuable resource and 500 gold for 1 desired valuable resource. It definitely wouldn't be cheaper than 500 gold, maybe more expensive.