It's the worst SP in the game, yeah.
There's others of similiar... "value", like +2 gold per your land route one. 16-20 gold max, and that's assuming you're drunk and forgot that such a thing as a "Cargo Ship" exists and it apparently gives twice as much stuff, or the +3 per trade route to other civs believing in Freedom policy, or +4 gold per cargo ship (not as bad, but still 40 gold very late in the game isn't good [it's IIRC the final policy of naval tree, which... is not really worth finishing, because all the good stuff is in the first two picks])