It can be incredibly confusing to really keep track of the various different types of 3D printing technology out there. Most people unfamiliar with the industry think that 3D printers are made with one particular technology, but in fact these printers feature 7 different techniques to build 3D objects. Based on your needs one printing technology will likely be more suitable to you than others. Having said this, pricing can vary substantially. Here is a quick chart which will show you the various different 3D Deposition processes, the Sintering methods, and the technologies and materials that can be used with those technologies. Hopefully this clears things up a little bit. The main thing to take away here is that 3D printers are not all created the same. Some of this technology is still patented, while others have had their patents expire. In addition new techniques are constantly being explored. Some abbreviations which are good to know to read the chart are:

DMLS - Direct Metal Laser Sintering
FDM - Fused Deposition Modelling
FFF - Fused Filament Fabrication
SLA - Stereolithography
SLS - Selective Laser Sintering
LOM - Laminated Object Manufacturing