No offense to you, Blair. But if you've installed "tons" of windows then it should be no problem for you to bid this job without any help from the forum. 50 windows X 4 hours per window = 200 hours? Over 2 weeks for 2 guys? I wouldn't plan on getting that bid, unless you charge $10/ hour. You did get some good info here though, like how long it should take a window professional to do the job.
I tell you what, bid it out at 200 hours x 50 = 10000 for labor. Then hire my crew to install, I'll only charge you 5000 and then you can pocket the other 5 g's and sit back and chill. It would take us 3 days tops to set 50 windows, and that's being conservative.

But only if
I measure the windows.
But hey. Good Luck with that.
BTW, I checked out your website. Very nice work. You look like one hell of a remodeler.