If you're in Oregon or California, it looks like the wages there are much higher.
Also, you're probably paying the company which manages the plumbers, of which the plumbers don't directly earn that.
If you're hiring a plumber directly, I'd assume it's a more experienced one running their own business. In addition to charging you $200/hr for the work, they're probably doing their accounting and business management, billing, ordering parts and equipment, replacing tools, and communicating with clients.
I could see that only resulting in 10-20 billable hours per week.
Also, if many of their jobs are paid in cash, it's possible there's a significant amount that is unreported to the agencies generating these statistics.