Carrying food with you is usually a healthier option than eating whatever you can find during a one-hour turn, it's more convienient as well. Instead of shutting the airplane down on a 45 minute break, so I can scramble inside to stand in line at the nearest fast-food joint, then experience the employees' surly attitudes, just so I can give them $5 to satisfy my hunger and increase my cholesterol, I can enjoy a healthy meal while I leisurely prepare for the next flight.
I'd rather take that untaxed per-diem money and invest it. I earn the taxable equivalent income of around $600/mo. Using the techniques mentioned in previous posts, I can save about $450 of that amount monthly.
Invested at even a meager 8% return, I can increase my net worth an additional $5400 annually...not including compound interest effects.
This way, I'll be prepared for the future strike, bankruptcy, medical leave, or furlough that so many of us experience during our careers. If I'm fortunate enough to make it to age 60 in this profession without experiencing any of those, I should have an additional $376708 to retire with, in todays dollars. This assumes an average annual return of 8%, and an average annual inflation rate of 3%.
Let's see...$376708/30 years = $12,557 someone is paying me every year to invest a portion of my per-diem, rather than spending it at McDonalds. That's the easiest $12,000 raise I've ever negotiated!