Just like desserts, few caterers make their own hors d'oeuvres. Those chicken satays and mushrooms in fillo at your shul's dinner? Probably bought frozen by the caterer. I saved a bunch of money for a party by hiring my own waiters and buying the same appetizers wholesale at the Appetizer Store online. The owner is very nice and he has an expanded line of meat, parve, vegan and dairy, many of which are quite good (note that most of his stock is not kosher; kosher items are OU and come in sealed packages; there is a separate section of his site for kosher products). Highly recommended unless you have time to make your own.