The sentiment is certainly appreciated , but it's something we actively decided to avoid. We do this for our own interests and don't really want people to feel like we owe them something or that we should work on their requests in preference to others because they've made a financial contribution. At this stage our costs are very small (CI server from @mlyle, autotown from @dustin, crash report server from myself, and hardware prototyping and miscellaneous extras, e.g. USB IDs. The most useful things people can contribute are feedback, testing of new things, (detailed) bug reports, documentation improvements, code if abilities allow etc.
TL;DR Very much appreciate the sentiment, but politely refuse, and hope you continue to enjoy!