There's a specific category of people who get weird about this on social media. Shorthand for it is "burrito taxi discourse". There's usually a long list of excuses, some of which may have validity, some of which are a bit stretched.

I don't know whether they're covering for their own insecurity or are just not prepared to accept that their own cooking is (necessarily) slightly worse than restaurant food even if it's much cheaper.

Personally I sit at the middle level of this; in the UK there's a decent range of fresh refrigerated ready meals ("TV dinners" to Americans?) which are more expensive than cooking for yourself but less expensive than takeaway. This is mostly fine except you need to pick the gymbro protein-orientated branding in order to get a decent percentage of vegatables. Somehow this doesn't turn up in burrito taxi discourse.

I think the myth comes from the upfront costs of cooking equipment and spices as well as expensive proteins like ground beef. If you cook with mostly starches like rice or potatoes and just some meat, there's no contest. The other thing that can make cooking expensive is buying too many different ingredients to make a fancy dish and having a bunch of leftover stuff that gets thrown out. But that's where soups come in.