worth one's salt
worth one's salt という表現は、「その報酬に見合った価値がある」という意味になります。
Any teacher worth his salt is able to inspire his students.
I'm confident enough to know I'm worth my salt around here. I make a lot of money for this company.
The expression to be worth one’s salt, which means you’re competent and deserve what you’re earning, is most often said to have its roots in ancient Rome, where soldiers were sometimes paid in salt or given an allowance to purchase it. The word salary is derived from the Latin “salarium,” which originally referred to a soldier’s allowance to buy salt.
(Elizabeth Nix. Where did the expression “worth one’s salt” come from? Ask History. October 15, 2014.)