How old was Mathieu de Costa when he died?

There is no widely known historical figure named "Mathieu de Costa". It's possible you are thinking of someone else, or the name is misspelled.

Could you please provide more information, such as:

* Full name: Is there a middle name or any other part of the name that might be relevant?

* Occupation or field of work: Was this person a musician, artist, politician, or something else?

* Time period: When did this person live? Knowing the approximate century can help narrow down the search.

With more information, I might be able to help you find the answer you are looking for.