an eight ball usually goes for around $170 - $200.

Are they talking about an eight ball - dope (i.e. crack?) or an eight ball in pool? An eight ball in dope was about $150 - $175. I have NO idea how much a pool eight ball is.

who invented eight ball billiards

Eight-Ball Andy was created in 1948.

Sinking the Eight Ball was created in 1998.

In eight ball, the aim is to sink your 7 balls followed by the eight ball (black). Your balls are either the bigs or littles. In straight ball, the aim is to simply sink 8 balls of any denomination.