We stay in hotels in Switzerland that offer bed AND
breakfast. Breakfast is paid for and is not a courtesy
offer. We have noticed a wide range of consumption
habits at breakfast from mouse like to trencherman.
Average quantity consumed must be well known by
hoteliers and I have always felt that room pricing
allows for the average observed.
I have seen several times food taken away from the
breakfast room, most often by those who have eaten
little at the table.
Perhaps habit and practice varies between countries
Just my observations.