Hi bluroses,
From the sounds of it, you're not so much looking for a caterer as a restaurant that delivers. I do a lot of non-profit work, and we'll frequently bring in dinner to feed 20-30 people for working meetings. Because my organization's rules prohibit funding to be spent on food for internal meetings, our volunteers take turns bringing in the food. Obviously, most people are price-conscious since they're spending money out of pocket.
In my experience, calling something a "box lunch" automatically adds a dollar or two to the price point. Quite simply, it takes more time for a restaurant to assemble and uses more materials. Platters and trays with the same amount of food cost less than if that food was assembled into a box lunch. And when ordering platters and trays, you can actually get away with ordering less food because most people won't eat some of everything.
At the meetings I attend, I regularly see dinners bought from:
Pizza Capri
Corner Bakery
Potbelly's
Maggiano's
Costco (**as I recall, they have a mechanism in place for handling charitable in-kind donations)
Bucca di Bepo
Chipotle (**seems to be a very community-focused company, and gives a lot of stuff to the non-profit I work with)
I understand that all of the meals have to come from the same company. If there's any flexibility in that, and if someone from your organization could bring some basics from Jewel or elsewhere, it will also save your budget. For example, a couple multi-gallon containers of water and paper cups will be less expensive than 50 individual bottled waters. And you'll pay less for 5-pound bags of apples at Stanleys than you'd pay if you get them from Subway!