they read cookies... to see if you have been to a particular site.. and usually mark their price close to the price you have seen at the said competitor's site..
I could recommend using incognito mode, or Firefox focus on a mobile device.. but sometimes even that fails..
because of late they travel site keeps track of IP addresses [or something equivalent] enough to identify that you had visited the site before... and hence you would be shown the same elevated prices..
I can confirm to the above.. set up android + firefox + carrier internet Vs fresh incognito browsing session on Linux and Firefox on a think-pad laptop...
the laptop session showed lower prices... I guess the reason was: there was some browsing history in firefox + android + carrier setup
then there is the issue of jacking up the prices for the same seat [even though you may not have had any browsing history].. as you head closer to the final payment page.. I guess its like.. "the customer had done their research and arrived to the said site for the purpose of booking.. and had reached the final stages of the flight booking funnel.. a 5% markup [or any other %age figure] will not be a deterrent to the customer.. the customer will surely go through at with the booking at this stage.. and cannot afford to back down... " or so goes the thinking.. of who ever designed this scheme..
would be nice to have some insider account of how these practices come up..
the above includes only prices shown for ticket.. and then there are other additional surprises such as 'convenience fees' random taxes and what not.. that inflate the final bill further
I got fed up with these tricks that i had decided to stick with Indian railways...fares are fixed.. seats are scarce... though honestly.. they are beginning to experiment and adopt some of the practices from the airlines industry