I know this web site is about working out if 1 mile equals $0.07 or $0.12, my personal philosophy actually goes against that.
Don't worry about $200 difference between Air Asia X and Singapore Air. Don't worry about 10000 miles difference between Singapore Air and Virgin Atlantic. These are really small amounts when you look at the total cost of a trip. Spend your energy on making every trip meaningful for yourself, worry about whether you should die sky diving or die in the cold at Milford Sound in winter., not $200 or 10000 miles. You will be thinking about your life, the time your have with your loved one, the fun you had, when your time is up. No one, ever, thinks about $200 extra they paid xx_ airways when they look back at their lives.