Investigating some some are to decide what to buy properly could be a couple hundred tabs easily. Usually you can close those when you are done, especially if you use Tree Style Tab to have them in their own little trees - but not always you have the time or are waiting to try the thing after it arrives.
Its is more tricky with technical projects, as you might and up with a big reference tab hierarchy that ideally you should first all read before closing it (maybe, just maybe, someone in one of those forum posts you opened in a tab without looking yet solved your problem!) or get back to the interesting tabs when working on the project.
Worst of all are fiction or world building sites... Like, you end up on some page on Project RHO or Orion's Arm or a WH40K wiki somehow and that page has links to some other interesting topics. And those pages have more links - oh, interesting!
Those can get to hundreds or even thousands of tabs easily and you just can't close them - they are just so interesting and there is that one topic/megascale engineering project/story you did not read to the end yet and you can always get back to it - as long as you keep the tabs open!
And lastly, it is a sort of a diary/history log - sometimes you see a forgotten tab tree you did not touch in a while - oh, right I was researching that thing, how nostalgic! :)
Since task manager has been introduced, making it easy to unload whole related tab groups its even easier to reach absurd total tab counts. ;-)