Why is retail pricing typically 2x wholesale?

So..... I gave up my trade shop job making a jillion pieces a day
and went into high end custom. 

Jo, I’ll bet you wouldn’t have pulled off the custom were it not for
the years of jillion pieces a day.

There’ s something very satisfying about spending your day on one
piece, one that you care about, one that engages you both manually
and mentally. And then after you’re finished with your symphony, you
get a big fat check!