It's not a marketing scheme, well not really at least. The different model numbers depend on what is included in the package. For instance, the LM900 does not include the Kitty Kabana and the LM920 and LM950 do. The models vary from location to location as well as what is included. Sometimes it is the carpet, and sometimes it is the paw cleaning ramp and odor absorbing carbon filters. Soemtimes it is cheaper to buy things separately, that is the only part of this whole thing that could be considered a scheme. Just shop around before and price the different products. Good luck!