Recently I got successful two time with Singapore Airline upgrade. The krisflyer points does not change. You get only the points by original points on booking not on upgraded class points. I upgraded from from Economy Class to Business class for flight from Dubai to Singapore. What I got was the seat in business class and the meals served was like economy class points from economy class. It is not worth the upgrade. I will never do such bidding upgrade. So Singapore airline is not what it use to be. A interesting note. English letter has 26 alphabet. SIA used 22 of them in their class. Only missing are G, I,O, X. Economy has 15 (Y B E M H W N Q V K S T P L R ) Business (J Z C U D) First F A. So many levels to confuse you. It took me 8 call (more than 8hrs conversation with customer service.) 3 emails with a period of 8 week to learn this. 90% of the time you have to remind them to get reply.
So watchful before you bit for the upgrade