Thanks! I'm glad you find it useful. It may sound weird but this is me being lazy. I didn't want to calculate profitability each and every time I decided to trade, so I figured it'd be easier to do this. I added the pseudo-formula above, which is fairly simple as you'll see.
For the sake of precision, there's an implicit assumption that a "Supplies_1 + Look_for_2" profit is equal to two "Supplies_1 <> Supplies_2" or "Looking_for_1 <> Looking_for_2" profits. It might need some weighing to properly adjust it (just a single parameter), but I haven't paid much attention to that proportion yet.
My goal was to find some circular trade route, but I think it may need to be done programmatically. Or maybe with some matrices product... Something I never thought I'd need.
Edit: Actually, I realized it's an ant colony optimization sort of problem, which is solved programmatically.