The extra $300 is a shame, but is relatively small compared to the other less tangible (and pax-variable) costs of starting from MRU. You might burn 3 extra days of your holiday getting there and out, and if you're NA based you give up the opportunity to head directly home - you give up either Asia or Europe as you pass through. And you're stuck with BA's POS capacity-controls when it comes to booking space out of there, although I haven't read any complaints about that recently. Thus the last time we ended at CMB, even though the price difference for AONE3/4 was the better part of USD2000, it just didn't make sense.