$3 donation is never going to get us rich, especially when the conversation rate for such apps are normally below 5% of the user base. The primary reason for asking donation is to measure and validate your idea. One of the way to check your market-fit is to who's freely willing to pay for it.

The other reason is to cover our Heroku cost ($7 per month) and any other costs (e.g. domain name, the time we put in making/maintaining it, etc.). Nevertheless, please can just ignore and continue using the app for free.

But thanks for the feedback, you are right about the message, we thought it's too long to describe it all, but we'll try to come up with a better and clearer message.