On a recent morning, Jack Luu parked his plug-in Toyota Prius in one of the most expensive lots at Los Angeles International Airport before flying off to a film shoot in Canada. The lot, where Mr. Luu leaves his car as many as 10 times a month for business trips, normally charges $30 a day.

But when Mr. Luu returned home three weeks later, he drove out, as usual, without paying a dime.

"That...