Gringotts has no known competition in the wizarding banking industry, and is most surely a monopoly in Britain. Given that the bank is, according to Rubeus Hagrid, the only wizarding bank in Great Britain, it stands to reason that the goblins would have a tremendous amount of power over the wizarding economy, as goblins are also the force behind minting the wizarding currency, Galleons, Sickles, and Knuts