Hi Nick and welcome to the Q&A Board!
Yes, lithium batteries are very expensive if you take a lot of photos, but they do last seven times longer than standard alkaline, are much lighter and have a long shelf-life. Forget using alkaline batteries in a digital camera unless you want to end up in the poor house or take only a couple of photos a week.
If you buy a digital camera that comes with a proprietary rechargeable battery (ie. made by the manufacturer), it is usually Lithium-Ion. You'll definitely want a spare but they can be expensive if you buy them from the manufacturer. Sometimes you can buy equivalent batteries online for much less price.
If the camera you purchase uses AA batteries, NiMH rechargeable batteries are a good choice. They are excellent and you can get anywhere from 500 - 1000 charges per set.
It is actually surprising how much there is to learn about batteries and chargers. I'm referring you to another thread at the Board for additional info. It contains links to more information that should give you a good understanding of batteries and chargers.
http://www.digicamhelp.com/cgi-bin/yabb/YaBB.cgi?board=q-b;action=display;num=1128702904
