I really hate that they don't fix these trading exploits, it absolutely ruins the game for me. I won't be officially posting a final for the latest 2 science games as I also found this trade "exploit" by accident and wanted to see what the heck was going on and don't think it is a fair comparison.
When I ran into an AI civ with over 150gpt turn output and I wanted to see what would happen with 100+ 1gpt trades (after already trading with a few other AI for ~60gpt this way) -- the game crashed. Basically if I offered everything I had to trade at once, I could get their ~300gold + ~40gpt, but using the trade "bug" I could trade FEWER resources for their ~300g + ~171gpt (except crash time afterwards).
The fluctuation is stupid annoying (to me). When I found the "bug" there was an AI that would give me 3gpt for 20 strategic resources, so about 4.5g per resource over 30 turns. However, if I made another trade first for (almost) all their base gold (generally down to 0-4 gold), the AI would start giving me 1gpt for 1 SR, so 30 gold per resource (vice 4.5gpr!!) over 30 turns. Absolutely insane. Even just programing it to round to 0 (for no trade) if too low would be a decent fix, but appears to truncate to minimum of 1.
A potential game fix would be to set trades so you had to sell strategic resources and diplomatic favor in sets of 10 or more at a time (or in sets of 10 if that is easier to code). This still provides some minor rounding to mess around with if desired, but not the insane game changing exploit that can be done now.
A potentially even easier/better game fix would be to only allow one trade to each AI per turn. This eliminates all the same turn rounding exploits that exist, but still probably allows some slow roll exploits that aren't quite so game changing.
Concur
@Monthar solution of no trades <2gpt would be easiest to check and eliminates the most exploitive trades, but really wish they would just fix the game mechanic.
And the maps for the last two games were absolutely awesome and surprising!