Well, we don't know what the sizeable amount was, do we? Whatever it was was obviously way more than what the job was worth, and Elektra was running a corporation and was probably some sort of billionaire so maybe the assumption that it could carry Matt for a while is wrong and it could actually carry Matt for years.

For me, Foggy not being worried about it flagged that he knew Matt was financially secure. Foggy's only concern is Matt backsliding into being Daredevil. If Foggy had every day financial concerns about Matt not being able to eat, maybe it would have come up? But since everybody had only one devil-shaped concern about Matt's life and health, I didn't think about his means either.