Kosher Catering L.A.
We recently did a Friday night buffet dinner using carryout from Sassi in Encino. We paid under $20 a head, and it was still way, way, way too much food. I should really know better, I eat there and I know what their portion sizes are like! This was a vegetarian meal, so possibly slightly less expensive than serving meat. If you are careful with the amounts you order, you could definitely do well.
You might want to consider take-out or drop-off catering, with you doing the lion's share of the work yourselves. Such catering costs basically the same as take-out food, but it's typically supplied in steam table pans which can be warmed (or kept warm) in your oven or on a steam-table rack over sterno flames. From a kosher restaurant which does such catering, the food would be supplied sealed with simanim, so that your guests could be assured of the kashrus of the product. The advantages are obvious- good catered food for the price of food in a restaurant, or even far less under some circumstances. For example, restaurants often supply more food than the average person will eat. Catering portions can be smaller, more reflective of average appetites, and therefore could bring the per-person cost to below restaurant levels, even factoring in double portions for some. I don't know about you, but I would rather rent a few tables, hire a few people for serving, and saving a bunch of money with $25 per person food, than pay $50 for the whole shebang. For a hundred people, that's $2500 difference, and I figure I'd save most of that.
Perhaps if you could add in a few details you will get a better answer. Do you need a venue or do you have one? What time of day will your event be held? Meat or dairy? Adults, kids or both? Do you need a bar or would juices and soda be fine? Do you have an idea of what you can afford rto spend. Some may say anything under $50 a head is inexpensive you may be looking at a slightly larger or slightly small budget. The more details you can include the more help you will get.
I am on the East Coast, so I can't be of any more help, sorry!