I would assume this is a chicken and egg problem if they're bootstrapping the startup. On the one hand, they probably need the fee to be this high while the amount of users is small so that they can sustain themselves and grow the business. On the other hand, something seems fishy to the end user when they see that such a huge chunk of their donation isn't going to the target recipient.
Some things that might make users more comfortable: 1)the declaration of what type of corporation they are and/or 2) whether they plan to reduce their take of donations as they reach certain milestones.
Some things that might make users more comfortable: 1)the declaration of what type of corporation they are and/or 2) whether they plan to reduce their take of donations as they reach certain milestones.