I think crowdsourcing would open up SWmonkey to 'attack' from SW, where SW would flood the channel with conflicting info at a rate that would make the SWmonkey site useless to legitimate customers.
Also, most of the companies that offer fare comparisons do not show SW flights... Some of those companies have the tech chops to implement 'fixes' that would comply with the SW site TOS and the massive legal departments to defend their position/approach in any and all courts in the world.
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.