The EN World kitten
Since I'm what my friends call "that guy," I couldn't help but count the squares once I saw your comment. As near as I can tell, the first floor has 244 squares, the second floor has 79, and the third floor has 39.IDK, that looks bigger than 1850 SF to me!
That's 362 squares altogether. Presuming that each one is your standard 5-foot-by-5-foot space (i.e. 25 square feet), then the place is 9,050 square feet, which I suppose makes that price tag a lot more understandable.
EDIT: Being a circle, the first floor is easier to calculate if you measure that the radius is 45 feet, giving it a total area of 6,362 square feet. Adding in the 118 squares for the next two floors at the usual calculation of 25 square feet each, and that brings the total area up to 9,312 square feet.