An economical analysis of palladium membrane reactors for the water gas shift (WGS) reaction is presented and discussed. In particular, a comparison of costs between the conventional apparatus and different membrane systems, for a fixed pure hydrogen recovery, is reported, The effect of the palladium thickness and of the membrane permeability to hydrogen on costs of membrane devices is analysed. Both higher permeabilities and lower thickness improve the hydrogen removal leading to a decrease in membrane area for a fixed hydrogen recovery and, thus, to a cost reduction. While both capital and operating costs are higher than the traditional ones for all the range of permeabilities used, by reducing the palladium thickness, it is possible to determine a range in which membrane reactors might be cost-effective. In particular, for palladium thicknesses equal or lower than 30 mum, membrane reactors could represent a possible alternative to conventional apparatus.