Singapore Airlines are government owned but commercially run, the idea was to make money rather than have a state subsidised, inefficient, poor service, jobs for the boys excuse for an airline like so many developing countries. Air India or Kuwait Airways come to mind.
The fares tend to be in the upper range unless you get lucky with a special deal but the airline is profitable so they must be getting it right.
Yesterday, I had a flight on a full service airline but budget economy ticket ie last class. The baggage allowance was 10kg rather than 20kg but I had no check in bags anyway. The wife and I ended up in middle seats in separate rows and got only 50% of the normal airmiles. No complaints at all and quite acceptable for a 1:20 flight. The fare was only slightly higher than a low cost and I needed to keep my account active to avoiding losing my miles, so it was worth it for me.