It shouldn't cost that much, but signalling is surprisingly expensive because pre-computerised signalling systems rely on large amounts of heavy equipment insta

It shouldn't cost that much, but signalling is surprisingly expensive because pre-computerised signalling systems rely on large amounts of heavy equipment installed trackside, and trains can't run without coherent signalling. So changing it can only be done in small pieces, small parts at a time, yet labour and equipment must be constantly available. For this reason the productivity of railway workers is quite low but unavoidably so; they spend most of their time just waiting for tracks to clear.