You can get cheaper ones on-line, but not always good ones. Printer mfg have learned what most mfg know, that its better to keep thier product price very low and make their money on the ink cartridges.
I have a canon, and have bought new machines to get the cartridges because it was cheeper than the two cartridges themselves.
If you can find a reliable ink dealer on the internet, thats the way to go. Unfortuantly, they're not all reliable.
Lanny