I age a friend that mined a bunch. They've sold some, kept some.

Basically, they're worth tens of millions, and they sell some, making them worth a few million in Bitcoin. Then the price goes up, making them worth tens of million again (In Bitcoin). Of course those others investments they bought from Bitcoin sales are also growing. 

 I know a guy who got some way below $1 and continued mining it before you need an ASIC. Built a great business and continues to put it to good use.

It's what I like to see.