Agudas Yisrael of America had their yearly convention at the Pioneer Country Club [a religious hotel in the Catskills - alav hashalom!]. One time it happened that someone rose and announced that the Rabbis don't have to pay because the Agudah is taking care of it. About 40 Rabbis left the hotel and 3 remained behind to pay: Rav Moshe Feinstein, Rav Aharon Kotler and Rav Yaakov Ruderman. They all came independently to the office and asked to pay. When they were assured that the Agudah had paid, they asked if the Agudah also tipped the workers. When Rav Aharon and Rav Ruderman heard that the Agudah took care of tips as well they left.
Rav Moshe was still not satisfied until he went around the hotel thanking the workers individually for all they had done for him.