Oh - I totally had the opposite interpretation; that the lesser civilization would gain much more (relatively) from the relationship. I mean, if I do a tech treaty with some impovershed nation, they're going to learn things just when I try to explain the concepts I want them to help me with .... similarly if I trade with a very poor nation, they get a pretty big benefit just from my nation's presence.
While we're on the topic:
A) Can non-aggression treaties be set to a certain amount of time and that factor into the formula - I'd pay extra for a 20 turn nonaggression treaty so I could run in, get the quest item, and run out.
I was thinking about this in the car today - debt and lending. Would be neat if Capitar coudl lend me 500Gildar and I pay them back at a rate of 5.5 G / 100 turns (550G payback) ... and that lessens their desire to go to war with me because I owe them money.