One of the funny things I noticed is that AI base the price of weapon tech on its research value, not on value of how many tech they would skip if they get it.
For example it was very difficult for me to get enemy Phasor tech, since it's expensive.
But when AI got Phasor II tech, it was much easier for me to buy it compared to Phasor I, since Phasor II is cheaper.
Also, I noticed that in AI routine computer player objects of geting both lower and higher tech in same trade.
But, for him, it's not problem if I sell him obsolete tech later, in next deal, for full price (although it's pretty worthless for him).
On the other hand, it would also object if I had for example higher Solidering tech and wanted to sell lower one too in same deal, which is ridiculus, since this is not a weapon, both effects of lower and higher tech stack.
P.S.
I hope developers read this, so it could be fixed in future patches.