I've taught and played this three times in under 90 minutes total each time. Two 3 player games, one four player game. More players definitely impacts the time it takes (more than linear increase) as there is more to consider, but 2.5 hours would seem to be a case of having multiple people with AP issues rather than the game itself.
Well, part of the reason it took so long is that we had one really long laughter break. This game produced one of the best unintentional one liners I have ever heard in a game. It happened due to the "remove a worker and choose to collect money mechanic". One player stated " I want to buy that building but I am too poor". Another player stated "Well, you could always yank a guy and get paid." OOPS!!!!!!!