I usually don't use them in that case,
I confess that I don't a lot as well, but I'm trying to raise my game in regards to following some of these rules
In this example I think
if (cost > 2x)Â digitalWrite(ledPin, HIGH);
Is neater, and allows you to see more code at a time on the screen. If you add another line you move them down and put them in {}.
Rob