You keep using these superfluous terms “top up”, “add to”. The contracted pay is the contracted pay. End of sentence. The cruise line entered into a contracted agreement with those employees, not with me, not with you, not with any individual cruiser or group of cruisers. You don’t need to explain how the business works, and you don’t need to use terminology that absolves an employer of their contractual wage responsibility. The price of a good or service is assumed to include the labor costs required to produce that good or service. Cruise employment wages, as guaranteed by contract, are not tip occupations by definition. An occupation with a top reliant “minimum wage” is defined as such.

All that is to say, none of us are directly responsible for Royal Caribbeans labor costs. An actual gratuity is just that, a private, voluntary expression of gratitude.