What cost? The hardware is dirt cheap. Programmers aren't cheap. The value of being able to use cheap software on cheap hardware is basically not having to spend a lot of time optimizing things. Time is the one thing that isn't cheap here. So there's a value in shipping something slightly sub optimal sooner rather than something better later.
> Except your browser taking 180% of available ram maybe.
For most business users, running the browser is pretty much the only job of the laptop. And using virtual memory for open tabs that aren't currently open is actually not that bad. There's no need to fit all your gazillion tabs into memory; only the ones you are looking at. Browsers are pretty good at that these days. The problem isn't that browsers aren't efficient but that we simply push them to the breaking content with content. Content creators simply expand their resource usage whenever browsers get optimized. The point of optimization is not saving cost on hardware but getting more out of the hardware.
The optimization topic triggers the OCD of a lot of people and sometimes those people do nice things. John Carmack built his career when Moore's law was still on display. Everything he did to get the most out of CPUs was super relevant and cool but it also dated in a matter of a few years. One moment we were running doom on simple 386 computers and the next we were running Quake and Unreal with shiny new Voodoo GPUs on a Pentium II pro. I actually had the Riva 128 as my first GPU, which was one of the first products that Nvidia shipped running Unreal and other cool stuff. And while CPUs have increased enormously in performance, GPUs have increased even more by some ridiculous factor. Nvidia has come a long way since then.
I'm not saying optimization is not important but I'm just saying that compute is a cheap commodity. I actually spend quite a bit of time optimizing stuff so I can appreciate what that feels like and how nice it is when you make something faster. And sometimes that can really make a big difference. But sometimes my time is better spent elsewhere as well.