In fact I would presume that the reason people are not going to pay up front is that they assume the developer is doing it as a favor to the community, and that giving them money for it would break the philosophy of giving out of free will. The real issue though seems to be an overall lack of resources. A one man shop, even with the ability to work on their projects full time, still has a maximum output capacity. Without others to assist there is the chance they would get swarmed with bugs and feature requests leading to burn out.
I think that open source developers need to step back and consider the costs and benefits of their projects. Doing a large amount of projects by oneself without a good job to support on the side will lead to burnout, as we've seen here. It may feel like bestowing a great gift on the community, but if you burn out and halt all development where has that feeling of contribution gone?
Which begs the question of which is more valuable: financial contributions or code contributions?