More than likely, 99% of that cost is the container and the apparatus to make use of its energy. [0][1]
[0] https://www.thoughtco.com/what-is-most-expensive-element-606...).
[1] https://www.sciencedirect.com/topics/earth-and-planetary-sci....
[0] https://www.thoughtco.com/what-is-most-expensive-element-606...).
[1] https://www.sciencedirect.com/topics/earth-and-planetary-sci....
It is very unlikely that the production of Pu-238 would cost less to produce than the container and the apparatus that harvests the energy.
Let alone the issues with the waste products of U-234 hanging about in the kitchen or basement. If you think climate change is bad as is, add in what people will do when faced with surplus uranium waste removal costs.