Yes, I agree, but it is a memory leak. It doesn’t START at 10GB. Also closing windows does not help much at all.
To answer your question, I have a total of 73 windows open at the moment. 11 of them are from applications with a single window open, 8 are from iTerm, and 54 are from Sublime Text. I am aware that is quite a lot for Sublime, but that is just how I use it.
Regardless, I just quit Sublime Text, and the memory usage only dropped to 8.9GB still absurdly high for having 19 windows open.
I too have the problem with WindowServer although for me it seems to happen with just regular usage. I have not rebooted in 48 days, and currently it is using 10GB RAM (I have a MacBook Air with 16GB). I have seen some people claim it has to do with using a display scaling setting other than the default (I use 1280x800).
https://gist.github.com/ccampbell/9a0118b0e3e607ec56a3a2cc59...