I suppose what we're looking for is the best tier point per pound ratio.
A F class return ex-LIS to the US east coast 440tp / £1500ish gives a 0.29tp/£
GUWonder said that he did two DUB - LDY returns in one day, netting 80 points for £156. This works out at a slightly better 0.51tp/£
I don't quite understand the JFK-LAX-SFO-LAX-JFK thing but that's about £500 for 640 points which is an amazing 1.28tp/£
Ironic that the best pt/£ would not be on BA, but a partner.