Maybe this sounds stupid as I don't know about Panamanian politics, but I would have expected that this is their most important source of income?
> The Panama Canal Authority is established under Title XIV of the National Constitution, and has exclusive responsibility for the operation, administration, management, preservation, maintenance, and modernization of the canal. It is responsible for the operation of the canal in a safe, continuous, efficient, and profitable manner.[1]
Emphasis mine
If that is wrong, naive or stupid I'd like to know.