I have education in the electrical field. Gold is a better conductor of electricity, as far as I remember. Copper is right up there but as copper is way cheaper, its the element of choice. The rest are snake oil as far as increasing power. Also at 3 times the cost longevity is non issue as well.
No, gold is not a better conductor. Gold is a good conductor, and does not corrode over time like copper, hence it is a better for metal contact-to-contact, such as connectors, electrical plugs, etc. However, for one continuous piece, copper is superior to gold, and silver is even better.
I used to think gold was a better conductor as well, because I had heard that, until I did some research. I will point out that the difference is so small, that a gold spark plug would work just fine I bet, but the cost would be terrible.
Here are some good reads.
Lets use Champion brand spark plugs from O'Reilly Auto Parts as an example:
Lets say a copper plug costs $2.29 and lasts 25000 miles. Thats $9.16. Over 100,000 miles and four sets, thats a total of $36.64.
Lets say an iridium plug costs $7.49 and lasts 100,000 miles. Thats $29.96.
Thats a savings of $6.68. If iridium works as well as copper in an engine, I'd say it was worth it. Less labor to change the plugs, and less cost in parts. And thats just for a four cylinder engine, if you up the plug count from 4 plugs to 16 plugs, like my dual-plug-per-cylinder V8 in my Dakota, the savings get even larger. I am going to disagree with you on the snake oil comment.
However, as pointed out by Fujative and others, iridium does not work well in all engines. Your results may vary, and platinum is definitely not worth it, unless your manual/engine calls for it.