 Which is why cruise lines are increasing the size of their casinos, building big onboard shopping malls, and adding fancy restaurants where passengers pay a surcharge of as much as $30 a head to dine. Traditionally, bars, casinos, and art auctions generated most onboard revenue. But now malls, spas, photographs, internet services, and phone services, along with bingo cards, are important revenue sources. Once, bridge and engine room tours and yoga classes were free. Not anymore.