Sounds more unethical than anything else. I am sure the staff loves getting the uninformed traveler that is used to leaving an additional 15 to 20 percent above and beyond what they are already getting in the original price. ANY restaurant on the French side that tries to change the norm are out for themselves...and won't last long when the word gets out. Looking at the ''short'' picture instead of the ''long'' will destroy them sooner than later. Especially in the age of social media.