Exactly, I love how @narthur put it. The difference between “paying means I failed” and “paying means I made a cost/benefit analysis”.
And other non-punish-y interpretations as well! Like this one: A derailment could be thought of as a random and unpredictable thing that happened. Rather than treat that as undeserved and something to be covered by fine print, I can just think of that as how Beeminder occasionally gets paid for the service it provides.
It’s a reframing where paying isn’t a punishment that you deserve or don’t deserve, it’s just a totally deterministic consequence of your datapoints staying on your yellow brick road or not. It still works both motivation-wise and money-wise because with that consequence in place, you only rarely derail. Your behavior is shaped exactly as you wanted it to be and the amount you pay for that (determined randomly by the universe, such as whether you’ve gotten injured or whatever might cause a derailment) is fair.
I don’t know how common it is to psychologically frame it that way (we don’t see so many of such people in support, for obvious reasons!) but I’m pretty 
about those who do. (It’s also very suspect and 
for me as a cofounder to promote that reframing though…)