One funny thing is most browsers also scales memory usage with the total amount of system RAM. IE will also stop splitting processes after a set number of tabs if it's a bit too many - depends on the system resources.
Haha, I wouldn't know how much Safari or Chrome use on iOS, as you don't get any sort of Status Monitor. There's a hidden force-quit system, but that's it.
On the desktop side of things, I've used Chrome for 3 days without closing any tabs to see how much memory it uses. With about 40 tabs open, it was using 3.5GB memory on my Macbook. The with everything else open, I was using 6.2GB RAM. Who says more than 4GB is a waste?