Could nuclear weapons be built at substantially lower cost?

I'm thinking in particular of possible peacetime applications to nuclear powered spacecraft, of the Project Orion type. https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) The idea here was that small atomic or hydrogen bombs could actually be used to power a spacecraft. There were a variety of obstacles here, but, actually, the main one was simply the great expense of nuclear bombs. Now, of course, nuclear weapons are extremely tightly regulated. Supposing those regulations were loosened. Supposing private entrepeneurs could develop new approaches to their construction and development. How much cheaper could businessmen build H-bombs, than the government? Because, effectively, we could argue that we've actually had "controlled nuclear fusion" for over seventy years now. The only real difference between an H-bomb and controlled nuclear fusion, is the size of the explosion. And, actually, we can build nuclear weapons with yields of no more than conventional size -- a few tons of TNT, or less -- which could be used for conventional energy applications like powering spacecraft. Of course, there are problems with radiation in nuclear weapons, and engineers keep claiming that they can develop a "no tears" approach to nuclear fusion, that if only we give them another few billion dollars they can provide unlimited energy, in a form that can be used along with Johnson's baby shampoo, in your baby's bathwater. This probably will not be the case. It may be the "nuclear weapons" are the only form of nuclear fusion we're ever likely to get. We just have to control radiation problems as much as possible, and make them as cheap as possible. So, how cheap could businessmen make nuclear bombs, for peacetime applications like space propulsion? I'm asking economists this question, from an economic point of view. I'll probably ask physicists and engineers the question, as well, from their perspective. Although, they may argue that they're doing the best they can, as it is.