I'm a chemist and about 2 years ago, we had to clean out this company that was bought out. The new company was donating everything to the university as a tax writeoff. The computers they had were too old to put to good use so we accepted them as a donation so the company could get the writeoff and we had to dispose of them. It was about 100 computers but I took all the circuit boards out of each one. I then spent the day in the lab dipping them into aquaregia, which is ridiculously strong acid. It strips the boards of their gold. After that, I filtered all my gold out. I got about 40 bucks worth of gold. Given that I probably used about 10 bucks worth of acid and spent 4 hours doing this, I barely made minimum wage that day.
But just as another poster said, if you can find an old computer from the 80s, they were much bigger and had much more gold content. I did the same thing with an ancient computer that was laying around and got about 500 bucks worth of gold out of it.