Well everyone plays this game different i find the combination of trading ( which now 400 coal-7gc, 400hwp 10gc 400marble 10gc on sandy cove sever is the price 4/9/12) and gold production give me enough gc to to upgrade most building to lv4 as and when i feel like it. If i have a bad day trading i know i can still make 800gc a day and not click a single button. and this comment 4 gold bars to 1 coin is the same for iron bars 4 iron ore to 1 iron block, but because its not gc people dont mind the cost.