I think silver is highly undervalued and should be at least on par with gold, maybe its boom is just a little bit behind gold?
I think you overestimate the value of silver.
I think he's talking about the entire market cap with supply taken into account. There's around ten times more silver above ground than gold. That would make it worth over $100 if it was on a par.
There's no point in making a direct comparison though. Most of gold's value is speculation and desire. Silver will forever be that little bit less sexy.