Ok sure, how much does that cost? First we need to invent the tech, and find a zone that is stable and won't leak, and we have to be super-duper sure of it, the

Ok sure, how much does that cost? First we need to invent the tech, and find a zone that is stable and won't leak, and we have to be super-duper sure of it, then you need to transport the dry casks there and lower them into the mantle. But the facility still needs armed guards "forever" so that terrorists or rogue states can't go and get some radioactive magma and use it as a weapon.