Hi there. I was just booking a flight from the LHR > US.

The price in $ was $1600 *(or so). I logged in to pay. I have a UK address. Once i logged in, my currency was changed. Fine.
It priced out in GBP at £1050 and T class.
I didn't want to pay with my UK cc.
So, I changed my currency / payment location to $$$ and got re-priced at $1950 and W class.
I can still get a cheaper ticket and T class if I pay in pounds

What is this?
Why did the same ticket go from $1600 to $1900 in about 5 minutes (and the fare class changes) while if I pay in £££ it remains the same???

I really would prefer to use my $$$ credit card but it is now more expensive...