Probably by showing you lower prices and then going “oops the seat is no longer available” the minute you try to book it with your personal information.
Simple, by defining the price for customers they have insufficient data on as max(price). Private mode and VPN are actually super easy to detect for someone willing to extract the maximum value out of you.
By defaulting to high until low is demonstrated?
By defaulting to infinity (not selling to the person at all) until enough info is demonstrated.
I can see that now.
"For an extra 15% off your final purchase, simply enter your social security number!"