Further to my rant about my printer I have at last found out how expensive ink is from hp - here is the link to the volumes of ink in 940xl cartridges - Cartridge volumes
This means that the 4 cartridges equate to 118.5 ml of ink - the "buy all 4 together" option on amazon uk costs 75.47 euro which converted today equals $103.79 us.
Ink from HP costs a staggering $875.87 per litre! I believe there are 42 US gallons in a barrel of oil and at $100 per barrel you could buy 367 gallons or .... wait for it .... 1393 litres of crude for the same money !
Yep 1 litre of HP ink = 1393 litres of crude ! - Now you know why it cleans the print heads so often !
I don't think I will be giving anymore of my hard earned cash to these robbers and incidentally, if you are a robber, don't risk going to jail for robbing the gas station or grocery store for a packet of smokes and a few hundred bucks - just go round to your nearest HP depot and rob 10 litres of ink - its worth nearly $9000 and you are unlikely to be sent down for pinching ink !