Here's the longest link I've ever seen. It the HP link to the cartridge for the 6540 Printer:
http://www.shopping.hp.com/webapp/sh...rch_request.do;HHOJSID=yZcxNxYLyfKzxS3d7jpQGnZSxkBLhFdsv6LxFTx28 rM1mTpl7W6h!-944899565?searchType=ink_toner_cartridge&inkTonerSearchQuery=cartridge&pageName=HP%2Bink%2Band%2BHP%2Btoner_land&Printer_Search_Query=&Cartridge_Search_Query=&printerOrCartridgeSearch=cartridge&locationOfSearchQuery=&returnUrlQueryString=&searchQuery=C9362W
Cost is $14.00 per for black ink. I rarely use color. A few months ago I ordered 4 black cartridges for about $60.00. Two day shipping is free. This is a much better deal than any brick and motar store.
Over the years, I've bought the refills, reuseable cartridge, etc. and haven't been satisfied with any of them (one ruined my printer) HELPFUL HINT: In your Printer Preferences, keep it set on "draft" to conserve ink, it really helps. Good luck