I've never had a customer report performance issues relating to memory usage or a market analysis that suggested we should improve memory size or disk space used in the binaries we ship.

What I have gotten are expensive bills for network bandwidth and cloud platforms when backends are too chunky or download sizes too large.

Which of the two do you suggest we optimize for, the one that costs money and gets complaints, or the thing people argue about on HN and Reddit but mysteriously never materialized in reports?

I think it has changed since Moore's law pretty much stalled on single core. Windows 10 runs fine on old Core 2 Duo with 4GB RAM and SSD.