Actually the worst cost is not a ruler marked in nm, a headset or an annual. You all need those. It's the stuff you buy during training while you have money burning in your pocket, thinking it will make you a better/smarter/more competent pilot, but you end up not using at all.
Loads of stuff like this in the typical pilot shop, from holding pattern computers to expensive "aviator" watches and sunglasses. I personally fell for the ASA flight timer which I never used in anger because it was too unwieldy but there must be thousands of pounds worth of "pilot" stuff lying in cupboards around the world.
Oh, well, maybe one day we can sell it off as 'vintage'...
