It really doesn't matter if the price is cheaper on one website or another, it's the airline that determines the price. Read Flighthub's terms and conditions. "All prices displayed on the web site are subject to change without notice until ticketed. In some instances, a fare may change after a reservation has been made. In this case we will contact you to advise you of the fare increase before we proceed any further." A lot of flight aggregators, (kayak, skyscanner, cheapoair, flighthub) display old pricing information. Prices fluctuate all the time and the issue is that a website may display a really great price that doesn't actually exist. You purchase the ticket, they email you saying "HEY THAT DOESN'T EXIST ANYMORE, WE NEED MORE MONEY," etc.

Google their reviews, and don't look at trustpilot or the ones flighthub displays at the bottom of their page because they are littered with fake reviews. Check out the tripadvisor posts about them, and there are a couple on reddit, too. They are a shady company that misrepresents flight prices and charges all kinds of silly fees because of their false information. Their tickets also come with way more restrictions and fees that you will never run across through the airlines. Also, if anything changes on either side, whether you need to make amends to your flights or the airline changes anything, you have to rely on flighthub to provide you that information. Doesn't mean the airline will do a stellar job at this, but you have to wait for flighthub to relay you the relevant information or vice versa

Use Google Flights to find airfare to Europe and never book through a third party. Whether it's getting the wrong pricing information or having to deal with horrible customer service, it's not worth it if something goes wrong. That's not to see the airline won't have bad customer service, but with a middleman it compounds the problem.