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?