Simple Question:

How many miles are required to upgrade from economy > business on TK between Istanbul and either Singapore or Bangkok?

I've checked the chart at: http://www.new-milesandsmiles.com/index_en.html

According to the chart it's: 45,000 miles.

According to the calculator 26,500 miles.

Can anyone explain?



Longer Background (in case anyone cares):

I am TK Gold (initially via a status match but have requalified for two years) but I have never actually flown Turkish Airlines as i'm Australian based.

I am looking at booking a multi leg trip from Europe (AMS most likely) to MEL via SIN or BKK and then back to Montenegro. Seems a good fit for a TK booking and I am keen to try them. I am sitting on about 40,000 TK miles and will likely have 20k more in the next few months. I can also buy a few miles if upgrades are good value but i'd like to confirm the price and (ideally) get a round sense of how likely an upgrade is to come through before choosing to book with TK.

Thanks!