Let me share the one bad experience. The company was using a refill "service" and they supplied a BUM drum. The drum didn't turn.
What happened next wiped out all the projected savings.
The gears in the printer stripped, jammed and the drive electronics failed. Since HP service was called and they found the refill cartridge, no warranty was in effect and the repair bill was nearly the price of a new printer.
If you get some toner and DIY this, don't overuse that cartridge. Toss it out after a few fills.
BEEN THERE, DONE THAT. PAID THE PRICE.
What have been your experiences with refilling laser cartridges. My info has been that they can be refilled once, and then must be rebuilt after that - a much more involved process with parts replacement.
The pro side is that you can easily load more toner with no adverse consequences.
I have purchased rebuilt toner cartridges from the Internet with no problems, but I have never attempted it myself due to the stock and parts that must be kept on hand.