Let's do the math, because dollars make no sense when talking about a metal: $10,000,000,000,000,000,000 dollar and $55,000,000 per tons. That's 182 billion tons.
Now let's see what
National Geographic has to say:
one geoscientist calculated that there are 1.6 quadrillion tons of gold in the core—that’s enough to gild the entire surface of the planet half-a-meter (1.5 feet) thick
Why bother with an asteroid, if the earth's core holds 8800 times more gold?
Because it's ''easier'' to mine asteroids in space than drilling Earth's core.
2900 km (1.801.97646 miles) to drill to the core. So far we have done 12 km (7,45 miles), and it gets more difficult as you go deeper in terms of high temperatur and pressure. Any hole you excavate will slam down, to overcome that problem is not possible.
Asteroid mining is hypothetical planning, mostly because of its exorbitant costs. Start ups have developed plans to mine those objects. When it becomes economically viable the age of space mining will start. Unlimited amount of Gold, iron, nickel, iridium, palladium, platinum and magnesium out there, perhaps new type of elements. Even NASA has been experimenting of water extraction from asteroids to support space travel.