Comment by Tuna-Fish

The same mechanism that lets you convert gold-197 to mercury does in fact work to convert the equivalent isotope (that is, 1u lighter than gold) of the element left of gold on the periodic table to gold.

The only problem, the element left of gold is platinum, and platinum-196 is not even the most common isotope of platinum, making up ~25% of it. You're rather unlikely to be able to make money on this.

(Not that you would have been able to regardless of the price of platinum. There are 3,000,000,000,000,000,000,000 atoms in a gram of gold, and a desktop fusor is going to generate ~<1m neutrons per second.)