It’ll partly depend on if you’re doing the work yourself or farming it out. Sending it to a bodyshop, and getting the work done correctly and to a standard the insures it’s safe means you’ll drop upwards of 20k in just the tub, with no paint or mechanical rebuild yet. And what you see probably hides other problems you can’t see, for example rockers are a three piece assembly. Since they’re rotten and the ends of the x frame are as well then you will probably find that all three pieces of the rocker assembly need to be replaced as well as rebuilding the A and B post connections to the rockers.
Personally I would say that unless you can do much of this work yourself and are not in a hurry you’d be better off either selling it as a parts car or parting it out yourself and putting the money towards a better example.