I don't obsess over living expenses. I just have low living expenses by default because I don't need much to be content, and like to minimize stress. Here are my consistent monthly expenses:
I live right next to downtown Austin, TX on the East Side. It's walking distance to everything I need and biking distance to even more. Great location, great city, great weather, with no state income tax. I pay $1,200/mo for my studio apartment, which serves my current needs perfectly.
The apartment building's included utilities come to ~$45/mo. Electricity ~$40/mo. Internet $40/mo.
I cook all my own food and eat a plant-only diet (vegan). Eating at restaurants is a rarity and only for social reasons, never for the food itself on my own. My recipes are on autopilot, so cooking and food shopping involve no thought. I buy groceries at Whole Foods for an average of $200 per month. That's $7/day for 2,200 calories of healthy whole plant-based food (complex carbs, fruits, veggies, legumes, nuts, seeds, etc).
Eating plants is cheap, who would've thought. I don't buy any of the pricey vegan animal-parts replacements or packaged snacks. Bananas/apples/oranges are my snacks.
I enjoy my food but treat it more like a utility towards my well-being than source of pleasure. Would be sad to become dependent on food for baseline satisfaction.
Being self-employed, I don't have a company health insurance plan. I subscribe to catastrophic insurance for $220/mo.
I spend $45 every 6 weeks for a haircut, so let's say that's $30/mo.
I walk or bike everywhere, so the default cost is $0, except for the occasional bike repair or $5 electric scooter trip.
Total Base Expenses
$1,780/mo –> $21,360/year
If my earnings went to zero, I'd be able to live for $21k per year, and sustain that for many years without income. And it would also be easy to spin up a new business/service that earns me this level of income with my existing skills.
This affords me a comfortable lifestyle with a lot of convenience, given my location. I don't have to live with roommates either. It's not my total monthly spend, as I'll average a couple hundred dollars per month in random things that I value. Books, or one-time purchases like a blender, computer monitor, etc. contribute too. If something makes me more knowledgable, productive (energy efficient), or healthy, I don't care too much about the cost. And of course there are also occasional expenses that aren't avoidable. The average excess above the required monthly expense is about $220, bringing average monthly spend to $2,000.
Setting the bar for required post-tax earnings at only $21k per year means I can do whatever I want for now. This complete elimination of money stress (i.e. safety/freedom) is one of the main points of money. The other is acquiring assets/resources, which is what I'm building up for. My base assumption is that I'll be able to scale up earnings to support a family in the future. Whether it's through a business windfall (sale), high earnings potential of my skills/experience, or just running a larger business by then.
Edit added in 2021:
I no longer try to minimize my monthly expenses like I did following the FIRE concept for a couple years. You can only reduce so much, but have unlimited earning potential when running your own business. I'd rather increase top-line than squeeze small improvements on a small expense level.
All I did over a couple years was realize how little I need to be content, and tend not to buy anything unnecessary. For now, I can do as I please, work on whatever, and know that whatever happens, I won't starve.