Scaring customers at the point of checkout?

I just booked a ticket on United Airlines. As I was going through the checkout process and I see this:

BAM! $597.20 Total bill! No way I thought the price was $277.20. My first reaction was to exit the browser. As you can see it is just a way to get you to upgrade to premium seating. I wonder if they A|B tested this? My gut reaction is that this can only lead to more abandonment rates?

I do like the fact that it is on its own separate screen. You probably don’t want to go back because you already invested a ton of time at this point (finding the right timings and fares).

I wonder if Flying Cart should introduce a 2nd screen at the point of checkout to see if people will upgrade to a higher package or pay yearly?