The real matter is what definition of 'pro bono' they're taking. Many lawyers defer payment (and won't charge if they lose) until after the completion of proceedings, however you still have to pay for disbursements (IE, filing with the court, photocopies of documents, etc) which can run into the thousands.

By the fact he paid cash and said he's not worried about getting the money back, I'm guessing he's not short on cash. Most people who are short on cash don't pursue legal action because they see it as costing too much.