While the interplanetary transfer network is real (https://en.wikipedia.org/wiki/Interplanetary_Transport_Network https://en.wikipedia.org/wiki/Interplanetary_T

While the interplanetary transfer network is real (https://en.wikipedia.org/wiki/Interplanetary_Transport_Network https://en.wikipedia.org/wiki/Interplanetary_Transport_Netwo...), getting a payload onto the network itself requires a large and varying amount of energy based on where your asteroid is located. And then once you've successfully gotten your giant rock of solid platinum to some Earth-Sun Lagrange point, you still need to manage its descent to Earth, and beyond the technical difficulties of trying to steer it precisely, the superpowers of the world are unlikely to be peachy keen on the idea of a private company having global orbital bombardment capabilities, which is going to be a political headache of its own.