Samsung MLT-D105L

Toner for the Samsung SCX-4623FW. RRP SGD$115. Rated for 2500 sheets. I'm not familiar with laser printers and issues like disposable/reusable print heads, what parts will be worn out by using poor quality replacement toner, resetting chips etc. so I'll just stick to originals for now. I sure hope this doesn't measure amount of toner left by pages printed though, otherwise what's the point of using toner saving mode? At least it should have a manual override so I can use the last pinch of toner. I know old toner cartridges are worth money though, wonder if I can sell my old one?