Probably because the architecture and engineering is only a small part of the cost, the things the architects design in are much more expensive to build.
The actual design of the striking granite-block construction with large windows on the coast may not cost all that much. But the materials and skilled artisans sure do.
The actual design of the striking granite-block construction with large windows on the coast may not cost all that much. But the materials and skilled artisans sure do.