tarsnap is awesome, but it's in no way a replacement for dropbox - their use cases and scenarios where you can use them are entirely different.

If anything is overpriced, tarsnap is -- or was, last time I compared prices. Also picodollars are a bit opaque.

I really wanted to use it and hoped it'd come out reasonably compared to alternatives, but I actually found none except buying a hard disk + raspberry pi myself and hosting it at a friend's place. That was cheaper by about a factor 2, which (at 3TB data) was too much to ignore for my student budget. This was about two years ago though.

Tarsnap's great but it's a backup service not a sync service and is very unsuited for use as a sync service.