You're assuming every backer paid 300. Some donated more, some paid less.
The unwritten deal was that the funders were backing a low-overhead, indie organisation.
It's like a pathetic jealousy of wanting to help a homeless as long as you know they are never going to be richer than you.
Often, when companies get big, the motives change from "making a great product" to "milking the user for more money".