While I'm personally fine with the $20 price tag, it does seem a bit steep for more casual users (ignoring the fact that they can also get it for free if they compile it for themselves). I wonder if this might hinder adoption. On the other hand, I think the value that Blink provides is potentially so large that it might make sense to get revenue also from donations (one-time or recurring).

Blink's value derives not just from the excellent design of the app, with highly accurate and fast rendering, or it's features (mosh, most importantly). To me, the way in which Blink really blows the competition (e.g. Prompt) out of the water its open source development process. As a beta tester, I have found Carlos to be highly responsive to feature requests and bug reports on Github. This gives me the feeling that as a user, I actually have influence over the features of Blink, unlike other software, where maybe I can beg Panic Inc via a tweet to implement port forwarding. I would be happy to donate something like $5/month to the continued and highly responsive development of Blink. I think true open source on iOS is so rare that we should make a point of proving that it can be commercially viable.