Describe someone who is not using what he/she own to its full potential

Picture yourself, the best driver within your group of friends and with a passion for cars, driving in a small Toyota along a narrow windy road at 60km/h. Suddenly after a bend you find yourself behind a Ferrari that is cruising at 35km/h. You shake your head while waiting for an opportunity to take over and tell your friend in the passenger seat "chi ha il pane non ha i denti".

This, in Italian, means that who owns a certain (usually valuable) commodity because he/she could simply afford it, might not have the skills to make the appropriate use of it, whereas who has the skills can't afford it. It directly translates to "who has the bread, doesn't have teeth", implying that who has the teeth, doesn't have the bread (this would usually be the person who is making use of the sentence).

Is there any idiomatic way to express this in English?

The best equivalent is To have the means but not the know-how.

See this link with Italian sayings about food.

Who's lacking in brawn makes up for it in brains also comes close to it.