More complex motor controllers may be used to accurately control the speed and torque of the connected motor (or motors) and may be part of closed loop control systems for precise positioning of a driven machine.
The street price for a gold bar is: 180-190 gp. The price in a specialty store is: 381 gp. If you buy from a general store, the price is 180 gp. If you sell to a general store, the price is 120 gp. In the Grand Exchange, the market price is 204 gp, 194 gp minimum, and 214 gp as the maximum price.
They can easily be purchased through online bullion brokers and can be purchased as low as around 3% to 4% over spot prices. Compare that to the premium for American Silver Eagles, which currently range from about 25% to 30%, and it's pretty clear that 1,000-ounce silver bars are way more cost-effective. It should be noted that 1,000-ounce bars are not weighed precisely. The exact weight of a 1,000-ounce silver bar generally ranges from 995 to 1,005 ounces.