Abstract This paper studies arbitrage-free financial markets with bid-ask spreads whose super-hedging prices are submodular. The submodular assumption on the price, or supermodularity usually assumed utility functions, is formal expression of perfect complementarity, which dates back to Fisher, Pareto, and Edgeworth, according Samuelson (J Econ Lit 12:1255–1289, 1974). Our main contribution pro...