So you got a refurbished HP PhotoSmart 7525 printer for a great price. (The 7520 is exactly the same printer! - only has a different model number) Good job. Your HP starter inks didn't last too long, so now you're looking to buy some new ink.
There lots of options out there beyond HP's exorbitant prices. I generally go on eBay and look for compatible cartridges. Usually the quality is good enough for my purposes, and you can save lots of money. Cartridge World is a good place to go locally. They will refill pretty much everything. Most Office Depots and Staples have refilling stations as well. Sometimes you can find deals on expired ink on eBay. As long as the cartridge is still sealed, they should work just fine.
Here's a site that offers 3 different solutions - Remanufactured, Premium replacement, and OEM - click here
Stock up with bundle packs and save! Time to make your own Christmas cards this year...