Ex EU is cheaper to compete for flyers with airfrance, KLM, Lufthansa etc which is not the case in the US. I have not found flights to be significantly cheaper on BA except in cities where it is clear there is a corporate contract (see BOS-BCN on Iberia or BOS-NRT on JAL for 8,000-11,000 routinely in J). The better comparison is to evaluate flights out of smaller cities in your area, or out of a DL or UA hub. For example, AUS-DFW-xxx is usually much cheaper than DFW-xxx because of the competition in AUS and lack of a fortress hub there.