Two things:

  Please understand that I'm talking about large
  trends here, and therefore when I say things like
  "nobody" I really mean fewer than 10,000,000
  people," and so on and so forth.

http://www.joelonsoftware.com/articles/APIWar.html

Also, I explicitly said "certain" B2B sales. Joel's conjectures about pricing and purchasing behaviour do not apply to everyone, just to those organizations that have a certain behaviour around making purchasing decisions.

Agreed! The world of POS and other small business database software is HUGE. The last non-coding job I had was working in retail and the boss had just laid down something like $25,000 for the worst point of sale system conceivable. Most of that was support, training, and installation.

That highlights a big issue, though - anything in that market will necessarily be a very high-touch sales process and therefore very expensive, unless it's absurdly easy to use and install. If you can solve that issue (Square seems to be having a crack at it), you'll probably be extremely successful.