If that weight were a fission reactor you wouldn't have to move it up and down. And it would be 100% efficient. And you wouldn't need an external power plant.
Climate change is urgent and we need all hands on deck to build as fast and as cheap as possible. May the best designs win asap in this fight!
A lot of the cost goes down when the reactor isn't a practically one-off build, and when you can for example use prefabricated components to "assemble" a power plant quickly.
Some designs go even further, and have power blocks that are essentially something you slap on large railcar, including option that instead of refueling you send back the module while the vendor sends you a freshly-fueled one.