Food is definitely something that you can save on by planning ahead of time. However, sometimes a lunch or dinner with a certain group of individuals, during or after a conference, can be well worth the money spent. While it is great to learn a thing or two at a conference, the networking is equally, if not more important.
I’d still say you can save by having one meal out with other professionals at a conference. A very simple way to save is to make sure you register on time. Many conferences increase their prices after a certain date.