isn't this called "catering"? I know some wealthy people who will often have catered food delivered (or prepared on premises) if they're having more than a couple people over and don't feel like cooking. this is also what my office does when they give us free lunch. I think the economics work out in a way where the per-head cost is pretty bad for 10-20 people, but reasonable for ~100 or more.
I think there are different tiers of service that are all called catering. when we get "catered" lunch at our office, they usually just put out a buffet of prepared food and we line up and take what we want. the catering staff will replace trays of food when they're empty and occasionally take your plate if you're finished eating, but that's about it. no idea what it costs per head.
no matter how you slice it, having other people prepare good food (ie, not pizza and wings) for you is relatively expensive. if you expect the food to come to you, it either has to be limited to dishes that travel well and don't suffer from sitting over heat for an hour, or you have to pay even more for people to cook it on location.
There are different tiers. Boston Market will cater which basically means putting their chicken and sides into 10-person party trays rather than individual meals. It's a good way to feed a very low budget wedding.
