I don't have much knowledge about that. However I read somewhere that, in order to convert and redeem krisflyer, besides certain number of miles we redeem, we need to pay the tax, which is around $800 if we fly to Europe.
$800~$1200 I can buy a return ticket to Europe already. So why do I need to accumulate miles?
Is there something I haven't seen yet?
1. Try flying within China or China to any place else. Its ridiculously expensive, miles are easily worth >3c per mile.
2. Need to buy tickets at short notice or not so flexible timeframe. Miles open up possibility and miles are worth 1.5c or more depending on where and when.
3. Longhaul flights with stopovers, you want to fly to USA and stopover at seoul for a few days, miles are easily worth 2c and above.
4. Biz class flights to anywhere. I won't even dream of buying biz class tickets but miles open up the possibility of traveling in biz class, miles usually worth 3c and above.
Above are just some of the situations where miles can come in useful and are worth the efforts collecting. IMO, only econ class to europe and those destinations covered by budget airlines might not be worth redeeming with miles else others are worth considering. BTW, taxes and surcharges for european destinations are around $500 only, don't know how you come out with the $800 example.