Hi, Johny. Good question!
TBH we weren't expecting to make anything from donations so it still gives us the warm fuzzies when people donate anything :)
Donations so far have been between 50p (about 67¢) and £35 (about $47) but mostly towards the lower end of the scale. The number of people who've donated represents around 1% of the total downloads so far (and the number of downloads averages around 50% of the page views). It all helps but it's not enough to cover our basic costs so we're in the process of figuring out about how best to address that moving forwards.
We haven't exactly promoted Autonauts and it may be that it's simply attracting as many people as it deserves. We do appreciate that it's still early days in its development and we haven't been too clear about where it's going, so that needs reinforcing regardless of how we decide to fund ongoing development.
Hope that's of some help. Happy to answer any more questions you might have :D