Are right of passige agreements a fixed value for the computer?

[tol'Sorahn]

Is what the computer is willing to give you for a right of passage dependent on the size of your territory? The reason I ask is that my civilization, although fairly small, was in the middle between two computers caught in a war and the Romans were more aggressive than the Persians who were playing defensively. You would think (well, at least hope) that the A.I. would reconize the strategic value to the Romans of being able to pass through my country 'legally'. But nope, they wanted me to pay ridiculous amounts of money for the agreement. When they wouldn't stop going through my territory, I declared war, and being the economic power of the time, I just paid 2 of the civilzations around Rome to join me in a military alliance. A few turns later the 2 hired civilizations made military pacts with 2 or 3 more civilizations so with about 5 or 6 other civs fighting Rome, I just sat back and built city improvements to combat war weariness (I was in a Republic), and let my friends beat Rome into dust. Rather humorous, yet I wish the A.I. could at least have seen the value in being able to cross my land.

Are there any variables for the value of a right of passage agreement?