I am looking at two one-way tickets (have to buy separately), one from L.A. to London, the other from Barcelona to Seattle for this winter. Dates are 12/24 for the first trip and 1/4 for the second and the price disparity I am finding is staggering. For reference, I got $1,140 (British Airways) for the tickets if purchased together. However, the LAX-LON leg is $380 (all on Kayak) and the BCN-SEA one is a whopping $1,634 (Delta; B.A. is almost 2 grand). Any reason for this discrepancy? Any way to circumvent it?