Windows vary by site, and I have 80 tabs opened. I have adblock plus, noscript and session manager installed. So of all the sites opened, there are less actual windows than without the extensions since I'm blocking the ads. Opening all the same urls in konqueror who has no such extensions enabled, I only have 444 windows vs 1465. That's less than a 3rd of the windows. 300% more windows than qt/kde has proved to be at least a lower bound on windows needed to do the job means gtk is being fairly wasteful, and this is with konqueror showing all the ads and flash firefox has blocked!
I might try this again later with the extensions disabled to see how much more windows I get.