I've been running a Canon i560. We bought 40 ink cartridges for $1 each in Goodwill - that's 10 black, 10 yellow, 10 cyan and 10 magenta. We have come to the end of the yellow and magenta almost simultaneously. We have 4 black and 2 cyan cartridges left. The blacks are double the size of the colours. This tells me that the tri-colour cartridges aren't as bad a buy as I would have imagined - even though they contain less ink. Oh yes and these ink cartridges have lasted us about 2 years. Not too shabby! As the i560 works well enough and we have an HP sitting unused in the garage, I can't imagine we'll be buying another printer any time soon - especially since the wife found 24 cartridges on ebay for $28!