That's got a "boil the ocean" problem. It's probably easier to imagine it on a per-flight basis; how many people in a set of people who may look at a given flight are going to be swmonkey users? You have to get that number above a certain threshold before that would work, but it's hard to get that number above a certain threshold because nobody will want to use the service until you're there.

Plus, with the way airline pricing works now, just because Alice sees one price doesn't mean Bob will see it ten minutes later. The faster the prices change, the higher the percentage of people you need to have crowdsourcing.

And I've just assumed that "crowdsourcing" looks like "install a browser extension". If it involves "typing numbers into another site" you can expect a participation rate indistinguishable from 0%. I've also assumed Southwest remains oblivious to this and never takes any actions to counter what they consider an undesirable use, which is also unrealistic.