There is more to consider than runtime exceptions. If it takes one-third or less time to write in Clojurescript, for example, this saves much cost. Even if you add in more runtime debugging, you still save time in writing code, and time saved in the compilation-fix cycle. Then of course, you save all the significant added time required in Elm to do non-trivial things with JavaScript libraries, which is inevitable.
One language isn't necessary better, but I do think one can be argued to certainly be less expensive.
Give two teams the same project. One team will use Elm and needs to write 20K lines and figure out some complicated JS interop. The other team uses ClojureScript and will need to write 5K lines and not worry about handling JS libraries. Which team costs more money?
