I just nearly had an expensive mistake with a booking on American Airlines.co.uk website.
I booked a single journey in the USA which had 2 sectors. The Y fare was £140 per person and the business fare was £229 per person. There were many timing options for the total journey and al the fares were a similar price. I booked 2 PAX on the business fare and progressed through the booking.
Just as I was about to pay with a Card, I noticed the final total was double i.e. excess £1,000. I placed the booking on 24 hour hold (a good facility!) rather than paying and obtained a booking reference number.
I repeated the booking for both the economy fare and the Business fare and the Economy final price was correct (£280 for 2 PAX) but the business final price was 2*2*£229. I took screen prints throughout the process.
I called AA with the anomaly and they checked by doing a dummy internet based booking.
They replicated the “error” and the person there took all my details and will contact me tomorrow.
Just as well I checked the final price before committing to the transaction. I am sure I would be laughed out of the shop if I came back and said “the price was lower at the initial stage of the booking”