A cheap operation is still infinitely more costly than no operation at all though. And not everything is on a local SSD, even just with a NAS, not to mention FTP, I really wouldn't want there to be no file extensions.
How would webdev look like? At first the HTML goes into "document", the style into "style", and before you know it, you're re-inventing extensions as prefixes or suffixes anyway, and I prefer users.sqlite to users_db. I honestly don't even see a problem to solve, so even the "cheapest" solution seems needlessly costly to me.
I don't see file extensions as a problem to be solved, either. My point is, it's nice that Linux (esp. Desktop Environment) ecosystem embraced magic byte parsing as a solution where having no extension creates problems.
I'm just happy to have the option around, I don't want to deprecate or against file extensions.
If you're interested, I can run some benchmarks on NFS and FTP as well, however.
How would webdev look like? At first the HTML goes into "document", the style into "style", and before you know it, you're re-inventing extensions as prefixes or suffixes anyway, and I prefer users.sqlite to users_db. I honestly don't even see a problem to solve, so even the "cheapest" solution seems needlessly costly to me.