[arthurptj]

Then why does every plumber I know own a yacht

[cucumber3732842]

Industry cartel.

If you landscaper had one like the plumbers do he'd have his own yacht.

Or he wouldn't exist because you'd buy about as much of his services as you do a plumber's.

[AngryData]

Because you live in a prosperous area and the plumbers unionized in order to maintain wage growth along side their neighbors.