I once looked a bit into long missions, rebalancing of rewards and such…it’s not an easy thing if you don’T wanna buff across the board and if you just shuffle stuff around people aren’t that much a fan of it. Either because they would refer a straight up buff to long missions and no cutting around shorter ones or because they think it’s suboptimal resource allocation…at least that I read from it.
P.S.:I think if you want a really bad mission cost benefit wise: Nightmare in dreampalace.