So you mean to say if we have unlimited supply of other metals like iron, copper, etc then gold prices will never increase!
No, things don't work like this.
Well let's not consider iron or copper which are not precious metals. What about platinum and silver? If all the platinum and silver in the world disappeared would the price of gold likely increase or decrease?
Even if Bitcoin remains #1 I can't help thinking that these alts are keeping the price down. I know a few guys at work who recently got into crypto currencies and they mostly started by buying ETH.