Look at gold. It has an atomic number of 79. Adding 1 proton would make it have 80 protons and that element (from the periodic table) is mercury. Look up the prices of Au and Hg and compare. Frankly, I would rather have Au (a solid) than Hg, (a liquid). Although Hg is rather expensive, I suspect Au costs more than Hg but you be the judge of that after researching the prices.

Question

just to check, would gold be more valuable if one proton was added to the nucleus instead of removing a proton.Adding a proton I think would increase its molecular mass therefore attracting a higher market vaue.