Many cartridges can be refilled two or three times.
You will not need a different toner formulation for each cartridge type but you will need about 15-16 formulations
to cover the majority of popular printers.
Also look into high capacity toner.
Here is a list of easy-to-refill, cheap-to-refill printers
http://www.inkfilling.com/cat-printers.html
I got the clp 300, works just perfect on 12.99 usd / 2000 page-yield per cartridge:
http://www.inkfilling.com/toner-refill-Samsung--CLP-300.html