Has anyone ever booked a flight with Google Flights? I am just wondering where they get their prices and data from, and if I might find a cheaper flight by using something like Expedia or Travelocity.
Google uses ITA Software's QPX software, which uses algorithms to combine and parse multiple sets of flight information from airlines. This includes any pricing and any other available data, which allows them to keep an up-to-date database that can be searched just like their search engine. This allows them to check against multiple different airlines for the various data that all of those programs like expedia and travelocity have access to. Refer to the information provided in the links to prevent for a lengthy post that is just quoted from the website. It is a quite complex and very effective software. You can read more on this topic on Google's website.
EDIT: If you're looking to find really good flights at a cheaper rate, Google has a good starting point for sure. I would potentially refer to websites like Kayak or CheapoAir as well however and then compare the prices. I always like to refer to multiple sources and see who offers the best rate. I usually always start with a Google search, this allows you to see what airlines might be the right one to go with in the long run.