Startup Idea : Pay it how you rate it

When we go on (luxury) holidays, for some extra or optional services (e.g guides, hotel gratuity, car rental, airport services...), I want to introduce a pay-as-you-rate method which let the person who receives the service judge how much he would be ready to pay for the service rendered (with a minimum amount imposed to cover operating cost and legal profit). I have seen that some people would be ready to pay a bit more than asked, when they are really happy or pleasantly surprised by excellent services. This will help persons to be motivated to deliver quality services, bring competitivity, customer delightness.