You asked: "would you buy "Billy Bob's Ford" (If I were the White Smokin' Pope of Billy Bob's Ford)."
IMO, this is a gut call. I'd review the SERPs and decide how well I own the top of the page (the name "Ford" can fire off a lot of PPC ads) While I am here, can someone explain to me why the name "Courtesy Ford" is so popular?
An interesting study to review would be a business that buys it's name in PPC. There hasn't been a study on how a shopper looking for "billy Bob's ford", that may have clicked on another link (PPC or Organic).
Regarding ROI, From my experiences, I'd wager these calls are often low to non-competitive SERPS that create service calls, or shoppers trying to reconnect with a rep.