Have you ever seen the movie Food Inc.? If you have, you will never want to eat meat again, or let your kids eat school lunch. Packing is so much healthier and economical (if you lay off the convenience snack foods.)
I will admit however that it is way easier to write a check and just let the kiddos eat at school. We were getting into that routine. It was the DH that finally took this area over and got us back on track. (Love that man!)
So this is how we/he runs it. The DDs are allowed to buy school lunch once a week. They get to choose the day. However, if they pack everyday for one whole week then he pays them $1. Our lunch bill has gone way down, and surprisingly the DDs don't complain about packing.