Is the leverage used in trading currencies, metals, and stocks, which multiplies purchasing power many times over, considered usurious, or is the purchasing process with it valid, given the existence of two different prices (a price of 3.75 riyals and an actual trading price of 0.375)?

It is not permissible to engage in leverage (margin) trading due to its inclusion of a usurious loan. The broker lends to the client to profit from commissions on buying and selling operations, and every loan that draws a benefit is usury. The resolution of the Islamic Fiqh Academy stipulated that the broker's condition to trade through him leads to combining a loan (salaf) with an exchange (mu'awadah), which is forbidden by Sharia.