Currently working on a similar app and I definitely agree that if you're going to be charging it should be towards a charity. This seems like a terrible cash grab with something that does not even provide an enticing service.
If you believe the point is to "make people feel bad if they fail" then you really deserve nothing from this. It conflicts with the stated purpose entirely. The goal should be to entice people to succeed, not punish them if they don't.
Edit: For reference, the original comment I responded to stated "If you charge towards the charity then a user doesn't feel bad when he/she fails."
To solve this, Stickk (a similar service) has "anti-charities."
StickK's list of 23 anti-charities (their anti-ness, of course, being in the eye of each goal-setting beholder) includes: The George W. Bush Presidential Library, the William Jefferson Clinton Presidential Library, the NRA, the Educational Fund to Stop Gun Violence, and various fan clubs of opposing sports teams.
I feel like your answer comes from you wishing to charge money for a product (understandable obviously) more so than it comes from any actual scientific or even observational basis.