What's up with all of the shady-seeming sites that Google Flights offers as places to purchase your ticket, typically at a price lower than directly through the airline's own site? If I saw this occasionally on a just a few routings from just a couple of online travel agents, then I might think that they're operating on the old bucket shop model ... but I see it on every single routing, and there's always a dozen or so sites to choose from. Are they legit? How are they able to undercut prices directly from the airline?