4100…
but I see what’s it’s trying to trick me into saying.
I just realized something.
When you put the mouse over the topic, you get a preview and the spoilers tags don’t show.
In my opinion, this makes it much easier to get the right answer…because (like I said before) people see ALL of the numbers in one place, so they’re apt to just add together all of the 1000s first (getting 4000) and then add the 10, 20, 30, 40 together (getting 100) and then just add 4000 and 100.
Go on, admit it if you did that. 
4100
4100
4100
I got 4,100 but I was being extra careful because I knew it had to be some osrt of mind trick.
4100
4100
5000
I get 4,100.
Why did you ask us this question?
4,100
Well, because so far about 11 or 12 people got different answers.
4,100
5000
OK, I got 5000, and I’ve always considered myself pretty good at mathematics.
But one could argue that real mathematicians don’t actually need to do this kind of routine summation any more often than anyone else. Their minds are usually on higher things.
I reckon that might it. I came up with my figure by highlighting a single spoiler box at a time and adding it to the running total in my head. If I highlighted (highlit?) all the spoiler boxes at once, I reckon I would’ve done better.
4100
5000
Edit: Damnit.
Without reading others 4,100.
4100
4100
Edit: Yes, I saw what you were up to, and I notice that the responders did pretty well with it.