Andrew Su, CEO at brokerage Compass Global Markets said the average cost of producing gold in Australia, home to some of the world's biggest gold miners, has jumped from $500 an ounce in 2007 to over $1,000 an ounce this year.
Persons (plural) is a very formal word. We only use it in rather legalistic contexts: [notice in a lift] Any person or persons found in possession of illegal substances will be prosecuted.
'Everyone is' is the correct version. Although 'everyone' sounds like a lot of people, it is actually a singular pronoun, and therefore requires a singular verb. Same goes for the indefinite pronouns everybody, anybody, anyone, someone, somebody, anything, everything, no one, nothing. You could probably think of it as a collective noun.