I'm thinking that the AI's cost estimates should be looked at again, wrt the Trade treaties/tech treaties/etc.  There seems to be a very real disconnect from what the output of the treaty is vs what they expect you (or they) to pay for it.

Whether or not they like you should be a bigger factor in the costing of treaties, rather than the relative military power between them and you.  Even then though, the relative output balance of the treaty should also factor into the costs.  Ie, if they are getting more out of the treaty than you are, they should lower their price, or pay you for it (if they like you).

For examples ---

Playing as an Empire (on Ridiculous), I can have the trades as seen in the below screenshots.  But they all cost ME gildar to create the trade treaty, even though the AIs are the ones getting the better deal.  In every deal, the AI gets TWICE or more gilder/turn, but still expects me to pay for it.  I expect that the bonuses for the AIs boost their output (along with tax rate).

Kraxis -- Our Power rating is 73-72 in my favour, but that's basically 'even'.  We do share a border (I've been border trolling them with Towns to take their resources), they are 'close' and we have a NAP, but they want me to pay for the treaty.

Monkey -- They have a slight advantage in Military power (73-77) and aren't my neighbour.  They are 'close' but expect 113 gildar for the trade treaty.  That is the same price that the Magnar want, but the Magnar are very much more powerful.  We have a NAP and a technology treaty (which they gave me gidlar for a while ago when I had more power rating than them).

Magnar - They are my neighbour and are much more 'powerful' (73-124), but want the same amount of gildar as the Monkey.  We don't have a NAP but are close.

Pariden - for an Empire vs. Kingdom comparison, they are a bit more powerful (73-87), only 'warm' with no NAP, and are not my neighbour.  They want more gildar than the Magnar for the treaty.