Searching for flights ABZ to LHR next May and thought I would take advantage of the $150 credit from my new Citi AA cards on purchases on aa.com. But when I search the flight on aa.com it costs $463, while on ba.com it costs £79 (~$123). I've never seen such disparate prices before on airline sites. Is this normal? The other sites (expedia/travelocity, etc.) all have prices similar to ba.com.