They're equivalent plans, but people have cognitive biases. Here are a couple of explanations from Propspect Theory:

- refunds are perceived as gains (against the reference point of the monthly charge), whereas a fee is perceived as a loss (and losses hurt more) - bills are capped so the the possibility of big fees (losses) is eliminated (people struggle with probabilities and fear extremely unlikely events)

http://en.wikipedia.org/wiki/Behavioral_economics#Prospect_t...