The scenario you describe with one tab using 20Gb is "beside the point" and certainly an exceptional situation. I've never seen that happen... I think I've had one Firefox crash this year, and that time it wasn't using all the RAM - it was hogging 100% CPU instead.

Of course the extra 2Gb might help for someone with less than 48Gb in their machine (most of us!).

Well, my point more was apps/sites that go sideways will eat as much RAM as they're allowed to. The 20 GB case was only special in that the leak rate was much higher than most. On a smaller scale, whenever my laptop fan kicked on, I knew I left a Travis tab open in the background somewhere. That was the CPU going into an aggressive GC loop due to the relatively huge amount of memory being used (2 - 4 GB).

But my original point is really that dismissing gross memory usage by saying you can buy more RAM for cheap is no longer accurate. In many cases, your machine's configuration is unchangeable. Getting an extra 2 GB RAM isn't $30, it's the cost of a brand new device. In other cases, where you might have configurable hardware, you often have to buy the largest capacity chip available and the economics get skewed. For SODIMMS, going 8 GB -> 16 GB is reasonably cheap, 16 GB -> 32 GB is fairly expensive.

I'd argue having to do a hardware upgrade for a web app in the first place is a bit silly. There's often very little reason for these apps to be so large in the first place.