Hi. I had the very same concern a couple of years ago. I decided to find which printer has the cheapest replaceable cartridges.
I already knew that inkjets are ink GUZZLERS whereas laser printers can go on one cartridge for years (for me at least printing on average 2 pages a day).
So I can only advise for black and white printers. I figure the rare occasions that I need colour, it will still be cheaper for me to take a graphic file to see someone else and borrow theirs.
I eventually found a great little laser printer...
an OKI B4100 available here: http://www.oki-shop.co.uk/index.php?section=products&dept=PRI&group=MLP&terms=4100
Their B/W cartridges cost between £20 and £35 pounds
Just google for "toner oki B4100" and you will find lots of people selling them. But two years in and I'm still using my first one.
The printer cost me £128 in Jan 2005 but I reckon that
had I bought an inkjet back then instead, I would have paid more money than that for printer plus many high-priced replacement cartridges.
So its done me well now for 2 years and still going strong.
However, if you can get hold of a Panasonic KXP-6100 or KXP-6300, or KXP-6500, then you are lucky b*gger. They are a bit old these days but my one (my previous laser printer) lasted for years - 5 or 6 I think. When it was finally on its last legs the repair man confirmed "they just don't make them that good any more". Brilliant it was. (Let me know if you find a second one on ebay or something and I'll pay good money for it)
Also I had a Dell inkjet for a short while and tried to get some non-proprietery ink cartridges for it. I came across "Hornet Computer Supplies" www.hornetcs.co.uk. They seem to specialise in trying to get round the tricks that Dell and other manufacturers do to ensure you use their own brand of toner. They've seem to have every toner design and ink-type covered to "get round" this "brand protection". One cartridge cost £5 and the one I got came with a syringe and a few other odds and ends to inject into the proprietary cartridge.
Sadly for me, Dell's system was too smart and totally ignored the new full cartidge. So it's not guaranteed, but worth a shot (unless you have a Dell)
google uk search: toner oki B4100