My suspicion is that it's partly about having a product worth $25, but also, and maybe more significantly, about having a company that is worth giving $25 to. I'd love to hear contrary examples, but it seems to me that the indie companies who do good business have pretty universally:
- Waited and patiently built up loyalty and recognition.
- Sold N copies/year at $25-$50/year.
I'm not sure it matters much whether the product is "worth" $25. A company like Apple could sell TextEdit and get $25 for it. Likewise the indie successes we know and love today, probably couldn't "make a living" on day one if they were coming out of nowhere and starting today.
Step 2 may be accelerated if you attract the right amount of buzz and or celebrity loyalty. Worth shooting for, but don't count it. Therefore my advice and personal strategy is: