Gradual change I'm working on that carries the greatest level of delicacy - very subtly encouraging DW to trim back her work lunches out. She used to bring lunches or stop home for lunch almost all of the time, but as her job responsibilities/stress grew, she converted to eating out at work basically every day, often with a friend or two. Since her pay was going up as well, and she seemed to be using it as a coping mechanism, I didn't object in any way. Over the past year I've been trying to whittle away at this cost without overtly criticizing or even pointing it out directly. More of a leading by example, but without any preachiness.
Some progress - she now seems to be eating at home 1-2 times per week, and actually considered occasionally eating at work (with her office door closed, as she needs some time to escape the incessant demands of her co-workers).
Man, those lunches get expensive, and as I've sliced our food costs elsewhere, they're really starting to stick out like a sore thumb.