Concentric castles were expensive to build, so that only the powerful military orders, the Hospitallers and Templars, or powerful kings could afford to build and maintain them. It has also been pointed out that the concentric layout suited the requirements of military orders such as the Hospitallers in resembling a monastery and housing a large garrison. Such castles were beyond the means of feudal barons. Thus, concentric castles coexisted with simpler enclosure castles and tower keeps even in the crusader states.