I sometimes dine from the "Wheel of Death" in the crew lounge. Okay, the vending machine that has assorted food. The sandwiches are about a quarter of the price of what's being sold upstairs and are pretty good sometimes. Sometimes even better than what's upstairs. Amazing how preservatives keep that freshness....
Every now and then they put fresh cut fruit in those machines so they stock it every day. Also, there's containers of milk for 65 cents which is much less expensive than upstairs.
Okay, that's the Eagle crew lounge and the AA non-rev lounge in ORD. The other airlines may have the same thing. Usually, the food doesn't last that long as everyone is buying it.
You can save a lot of money and some of the food is pretty good.