Happened to me more often than I can count. Always the same outcome: I work my normal speed, work gets done insanely fast, employers denies raise and points at me doing thigs for free, I stop working as far as I can legally get away with, employer needs to hire more people for the job I did before, I sabotage as much as I can, then leave.

In very rare occasions I got a little bit of extra money out of it but mostly i just learned a lot and switched jobs. went self employed later and did away with that shit.

but the system is a pile of shit, no matter your skills.