What does "no están de más" mean?

Question

Context

Juan is looking around the house for clues. He then displays the things he found on a table. Among the things he found are two coins. He picks them up and says:

Pero bueno, diez pesos no están de más.

What does this phrase mean and how is it used?

Answer 1

Estar de más means to be superfluous or unnecessary, so your sentence, which conveys a slight jocosity or sarcastic tone, can be translated as "10 pesos don't do any harm".

Answer 2

It can also mean "10 pesos more or less wont make a difference/impact/any harm".