No, gold bars are a commodity in the game that you cannot use real money to purchase more of. They are simply gained through gameplay. This is contrary to V-Bucks, which allow players to make cosmetic changes to their account, including buying new heroes to play, changing their melee weapon, the color of guns, paraglider, etc. But it makes sense since gold bars can only be spent during a match, that the only way to loot more to it would be in a game as well.