If the sculpture was cut into pieces to be cast, it is welded together and weld marks ground off. The welds create bumps and a dark rainbow hue on the bronze, and these nubs and color are also ground off. At this point, the bronze is a bright brassy color. The recesses are left with the majority of the patina and thus help define the shape of the sculpture. Molten clear paste wax is then applied, the piece is mounted on its base, and you have a finished bronze.
People often wonder why bronze is so expensive.
Each step of the above process requires an experienced artisan. Mold-making is an art in itself. So is wax pouring, wax chasing, bronze chasing and patina work. That's five different specialties right there. The wax is burned out of the investment, so the investment has to hold up to the bronze pour or the week or more of preparation in creating that investment is lost.