In GotM 116, there was Persia on the other continent, with no safe route to my landmass. According to the power graph i was about 3x stronger than them. My military was also stronger.
I sold them a tech for their whole gpt income. A few turns later, they made an outrageous demand and declared war upon refusal.
I remember the same thing happening in at least two more circumstances, but it's long ago and i don't remember the details.
I have the distinct feeling that when the AS get hard goods for gpt, they're more likely to demand and declare upon refusal. The AS seem 'smart' enough to factor in the broken gpt deal and 'realize' that it would be a win-win scenario for them.