Comment on ‘The Valuation of Contingent Claims under Portfolio Constraints: Reservation Buying and Selling Prices’
The pricing of derivative securities in the presence of market frictions has always been a question of fundamental importance. The reason is twofold: market frictions are present in numerous practical applications and, in such settings, the classical valuation theories break down entirely. Examples of market frictions include among others, transaction costs, non-traded assets and portfolio constraints. Alternative valuation criteria have been proposed and a variety of methods have been developed in order to define coherent derivative prices and, ultimately, to specify the hedging strategies. Three main valuation methods have been developed up to date: the superreplication approach, the imperfect-replication method and the utility maximization theory. The super-replication approach looks for hedging strategies that super-replicate, instead of replicating exactly, the payoff of the derivative security. The motivation for such a pricing mechanism comes from the fact that exact replication might result in an infinite derivative price, like for example in the presence of transaction costs (Soner et al., 1995). The imperfect replication method allows