Airlines ABSOLUTELY change their prices if you repeatedly check routes to a city. I have watched them change by over $100 over a few hours a day when contemplating a trip using their flight searches.
I now do all the flight route and time checking with a browser private window, no location being served, and VPN with an exit far from where I am, then use a phone on a cellular network to do any booking or vice versa in order to prevent tracking or some sort of identifying hash they might grab.
It's such a cheapass scam to basically gouge a customer based on interest.