I think the value of any Paso you'll find will be in what someone is willing to pay for it. Since they were only made for a handful of years, the year is somewhat negligible in my opinion. The differences you'll find are in whether you're looking at a 750, a 906 or a 907ie; if it's a 750 whether or not it's red, blue or white (Limited); and of course what kind of shape its in - and what the current owner is willing to part with it for ...
I think you'll find the 907ie's go for more than 750s and 906s will, especially given their limited run and more recent model years, and 906s more than 750s. However, if you find yourself a Limited 750, that may fetch more than standard 906.
For some idea on Paso production numbers, which will give you an idea of how many of what was made and when.
Otherwise, taking a guess? I'd say you could expect to pay $2500-4000 USD for a 750; and at $4k it would have to be exemplary. Mileage aside, we're still talking about a bike that's at least 15 years old, so I'd be more concerned with its maintenance and overall condition than I would its mileage.
I'd guess you could expect to see a 906 for $3000-4500 maybe? And a 907ie for an even larger range. I can't speak to either the 906/907s with as much confidence as a 750 though.
They're out there - this is a great site to help you in your quest, too. Good luck and keep us posted!
Jake