If the tech you want to trade keeps going down in price when you try to sell it to them, then they're researching it.
In other words.
Turn 1 - You see how much Egypt is willing to give for Iron Working - 100g let's say.
Turn 2 - Now they'll give 80g.
Turn 3 - 60g.
Turn 4 - 40g.
And so on. If your tech you're researching (say, Construction) goes from 12 turns, to 5 turns, then some AIs probably researched, or got that tech from a trade/goody hut.