The other technique not mentioned here is for buffets to just stop refilling the higher cost items on the buffet if a group of big eaters comes in. then let them sit empty while the diners fill up on potatoes or what not, before finally refilling them.
Salt makes food tastier and motivates you take another bite, which continues the cycle, so it's a good choice to put in the cheaper food by calorie/mass/volume/whatever-creates-satiety.
