Originally Posted by
lhrsfo
UA often has different fares for LHR-SFO return on the US site and the UK site. I simply book whichever is cheaper. However, you have to pay with a card with an address in the relevant site’s country. The OP has simply used the workaround that has often been discussed here.
That's just POS differentiation (point of sale, not the other POS)
Different pricing/fare buckets depending on billing country / point of sale
There are resident-only fares which go further than POS, as described by this thread. How often are those restrictions enforced? Ymmv