HP, literally, makes all their money from cartridges (inkjet, laser, etc). Don't look for big price decreases from them.
The best options I've found:
1. Use "$ off" coupons at places like staples, combined with other purchases (usually "free after rebate" items) to get the cartridges much cheaper.
2. Buy aftermarket refills/replacements (a la 123inkjet...)
3. Refill them yourself.
4. Buy "cheap after rebate" printers and strip out the catridges.
You can't really count on #1 or 4 on a consistent basis, so if you use a lot of ink (like I do, with 8 kids) you have to go with #2 or #3. I refill myself, even though its perhaps the task I hate the most, because even at $15-$20 per its a lot of money for me.