If you ask me there is a direct correlation between cost and comfort in a harness, but if you can't afford the bucks, here are a few suggestions. Firstly you can simply tie one with a cheap bit of 4 inch tape from your local climbing store where you could get enough for a harness from about $10, add a carabiner and you've got yourself a harness. It's cheap, it's nasty, with no padding and it will really hurt if you take a whipper, (if your going to lead i wouldn't recommend it) but it should be okay for the climbing gym, top roping or abseiling. Once i get some pictures I'll post a step by step guide on how to do it.
Since I haven't bought a harness for a while I asked the newsgroups for advice, and below are the responses I recieved,
Really depends on what they want it for. Really harnesses can start under $65 but that's your basic tape fully adjustable job. If they're looking for something with padding and gear loops prices jump to at least $140.
The ones made in the Czech Republic are good, and you can get a full adjustable padded CE approved for about $110 at Mountain Designs,Bogong and other
places probably. You can also get non padded adjustable ones starting at about $70.
The Singing Rock ones seem OK, not really well padded (mammut, arcteryx etc) but are comfy as the waist belt is seriously wide. Takes the price back from a "typical" $150 to $110 - $120. The very basic, unpadded, fully adjustable onse are $60-$80 and can have some great features such as the permanently threaded buckles which is a nice safety bonus for beginners. For the record I actually work for Mountain Designs (just to alery to any "vested interest") but also for a rockclimbing instruction and adventure trip company in SA, based on outdoor stuff.