I've thought similar things - Coda hasn't kept up with my progression as a developer - but after speaking to our designer at work I'm not convinced they have a problem. Coda is not for people who do full-time software engineering - it's much more targeted at designers, people who are iterating rapidly, possibly for clients, and for whom FTP is a perfectly reasonable deployment mechanism.

Unison is niche, but the only good piece of software in its category as far as I'm aware.

And Transmit is one of the best pieces of software I've used. I unfortunately have no use for it, but many people do.

Finally, I'm pretty sure that Firewatch did ok, so I'm sure that's some funding for them too.

I think Panic are in for the long haul. They're never going to be 'huge', but I think they're going to be financially successful for years to come.