A typical inkjet cartridge prints around 190 pages. So at 15 pages per $1 this is like buying cartridges at $13 a piece, except way more complicated and obnoxious. Cartridges normally cost around $20 so it is still a slight savings if you're willing to deal with the hassle of counting your pages every month.

For me however, I give that whole plan a giant middle finger. That's way too much headache and hassle for a $7 savings.