UV exposure kit, plus ferrochloric acid, plus container, plus some transparencies, plus some boards, will run you at about $150-$200. This will make pretty decent boards, and the consumables are cheaper than the prototype board maker costs per design, but if you want many copies, this becomes inefficient quickly. (The idea is to print the circuit to transparencies, then expose the boards using UV through the printed transparencies, then etch -- this is a little more robust than laser toner transfer)
A Dorkbot/PDX member makes regular orders of boards, where you get three copies of a design for $5 per square inch. The process takes about 2-3 weeks. Laen (who runs the batches) seems like a nice guy: PCB Order
You can sub out to China, which also takes about 2-3 weeks. People on this board recommend itead: http://iteadstudio.com/store/index.php?main_page=product_info&cPath=19_20&products_id=508
This is just under 2x4 inches (50x100 mm), 8 copies of the board, for $25 + shipping (which is $25 for DHL).
You can use ExpressPCB to make boards in the US with quick turn-around. The boards have to be exactly 2.8 x 3.5 inches, and cost $51 without soldermask for three, plus $10 shipping. It looks like turn-around can be pretty quick. http://expresspcb.com/ExpressPCBHtm/SpecsMiniboard.htm