The come for as littel as $300 but the build platform is very small. So you should probably consider the size of the objects your likely to produce and base your purchase from there. Do an internet search for 3D printers and you will find plenty of options between $400 and $1000. Often the cheaper ones you have to put together on your own and buy the parts individually. I.E. you can find the plastic bis as a set but you may have to find the hardware, motors, controllers and software from many different sources. Making it a poor choice for anyone who doesn't have some electronic and mechanical background. So figure out what you want in a 3D printer. Then come back with that list and we can better assist you. Or we can point you at the more commonly known systems like the Reprap.