From my head on steel buildings homes
One truck can deliver all of the materials you need, so the transportation cost is lower. The other way it manages to stay affordable is that it does not require a lot of manual labor to assemble. A team can be sent from most Quonset hut manufacturers that will come and assemble the Quonset hut in a matter of hours, unlike the manual labor for other styles of construction that need to be hired for at least a month. Once you factor together the cost of materials, the cost of transportation and the cost of assembly as compared to masonry or lumber you start to see how much more affordable an option a Quonset hut is. The fact that a Quonset hut can be easily moved made it a great tool for the Army during the second world war.