I recently spent 140,000 BA miles on a return to Santiago, Chile as follows;
LHR-JFK - BA First
JFK-SCL - LAN Business
70,000 BA Miles + £285 taxes
SCL-JFK LAN Business
JFK-LHR BA First
70,000 BA Miles + £111 taxes
Good value given that BA First LHR-JFK is 75,000 one-way, from my limited understanding of BA miles redemption rates.