Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Expensive and hard to find

The suspicious side of me wants to believe that HP did a promo with their Deskjet 612C - i.e. they sold the printer cheap or with big rebates as part of a system deal and decided to make up for their loss leader by limiting production and raising the price on the cartridge replacements. I would be surprised if there is any difference between the 612C black replacement cartridge C6614 and the much more common cartridge for the 660C other than a little plastic tab on the cartridge case.