‘Sell/Buy/Date,’ an exploration of the sex industry, is a must-see one-woman marvel

The writer and actress Sarah Jones is gorgeous, about 8 feel tall (at least it seems that way) and rail thin, with a wide mane of hair. When she walks onstage at the Geffen Playhouse, where she is performing her one-woman show “Sell/Buy/Date” through April 15, it’s impossible to imagine her hiding…