It's 1120 AD, turn 173, and I'm desperate to buy niter. My ally Arabia has plenty. If I ask them what they want for 1, they say 7 gold. If I ask for 2, they say 6 gold + 1 gpt. If I ask for 3, they say 3 gpt. If I ask for 4, they say 5 gpt + 2 gold. If I ask for 6, they say 8 gpt. However, I have no problem buying one at a time, at 7 gold, which would be 42 gold for 6 niter. I could then "buy" 42 gold from them for 2 gpt. The only thing I cannot do, buying one at a time, is buy when they have less than 40. But if I'm willing to pay the nonlinear premium, I can. It's purely annoying to buy one at a time, and forcing the players "in-the-know" to do so is user-unfriendly. Make the pricing linear. (Or maybe the right property is "associative"). And either disallow AIs selling any number so they end up with less than 40, or make the price for THOSE much more expensive (e.g. 7 each down to 40, 14 each for the next 10, 28 each for the next 10, etc. so if Arabia had 50 and I asked what they wanted for 20, they'd say 70 + 140 = 210). P.S. I'm fine with the price for per-turn resources, like luxuries, in gpt + gold, but I feel the price for immediate resources, like strategic or diplomatic favor or Great Works should be in gold. Yes one can borrow gold for gpt, but at a premium, and not everyone is willing to lend it, and there may not be enough gold to borrow. The risk of gpt transactions is one side might renege by declaring war, especially if they were planning to anyway.