Studies show that adding usage charges and other metered billing type pricing models can be very lucrative. This could be true for large web hosting companies and cellular phone carriers but startup businesses will most likely find that more complicated pricing will negatively effect sales conversions. When selling SaaS, the simplest plans win. Take a look at a few of the leaders in the market for example: SalesForce.com and 37 Signal's BaseCamp. Additional add-ons, m...