If you haven't tried replacing toner without replacing cartridge (the only way to achieve this level of cost efficiency), there may be some intermediate steps that are good to know about:
https://youtu.be/HaGQlP23Fqc
If you haven't tried replacing toner without replacing cartridge (the only way to achieve this level of cost efficiency), there may be some intermediate steps that are good to know about:
https://youtu.be/HaGQlP23Fqc