Originally Posted by SingaporeDon

As you know, buying miles with cash and miles options starts of at 3 cents per mile but gradually reduces as you decrease the miles required and increase the money part. However, there is a sweet spot, just before you reach the final 40% miles, 60% cash point, where the average cost of miles purchased comes out t 1.5 cents. The cost per miles then gradually increases as you get to 40 miles, 60% cash point, and if you go for this maximum option, your average cost per mile purchased is about 1.57 points

Hope I did not confuse you with all this!!!