Eating out is like the devil to financially savvy people. I can't believe how bad of a reputation its gotten, when in reality it hardly makes a difference to your finances. Here's the math on a hypothetical situation:
You can get a decent lunch deal for $10-15. I don't mean Maccas or any other fast food - I mean a freshly prepared chicken salad, or butter chicken, a few plates of sushi, or even some lamb tandoori. At an average of $13 a day for 5 days, you're out $65 a week for buying lunch.
Now subtract the total cost of 5 days worth of raw ingredients to make the meals yourself. You're looking at least $20. Factor in another $15 for electricity and water used for cooking/cleaning. To make your own lunch for those 5 days, you would spend around $35.
Congratulations - you're saving $30 a week by eating in. That's about the average person's full-time hourly wage. How long would it take you to prepare the meals yourself, heat them up, and clean up afterwards? Probably more than an hour.
For someone on hourly pay with a busy lifestyle, accounting for overtime rates, that extra hour could've been spent at work which would yield you at least $45. So accounting for time (which is just as valuable as money), you're almost better off buying your lunch if you can do it strategically.
Feel free to neg me if you own 7 houses by the age of 23 by giving up your avo on toast.