It was actually a simple round trip, and the itinerary with the first class segment was cheaper than other all-economy itineraries on the same and other airlines. Since he was only looking for the cheapest ticket, not specifically for first class (which he did not even realize until checkin time), the airline could have offered the same fare as an economy ticket and still made the sale.
Again, it sounds like jealousy, and as we told you, that's not the way it works.