There’s a lot of very good points here. A few things worth noting:

• I did factor in spoilage
• fuel costs are not going to even make a dent unless you live an hour from the store and are making grocery runs every day
• You’re definitely right that scale matters. It’s harder to make meals for one person unless your good at managing leftovers
• You’re also right about sushi. Anything that is that highly specialized with diverse ingredients that spoil quickly is going to be a pain to do yourself. I’m assuming for most people that are concerned with costs, sushi is more of a rare treat and has little in common with their average meal
• “time often does equal money” — I would definitely challenge this point. For most people it’s clearly wrong. If you have a salary it doesn’t help you to save some time on cooking because it has exactly zero impact on how much you make. Even for the people for whom time actually is money, it’s unclear if cooking will hurt their income for three reasons. One, the break they take to do something with their hands might actually make them more productive next time they sit down to concentrate, two it’s not clear that cooking takes more time than eating out. It probably takes more time than ordering in, but going out to a restaurant (especially a sit-down restaurant) involves a serious time commitment. Third, choosing where/what to eat when eating out is seriously draining. People for whom time really is money need to pare down the decisions they make to have something left in the tank when it comes time to make decisions that affect the bottom line. I’ll also mention that earning more is a very different strategy than saving. I’ve written about this before, but the right move for most people is to focus on reigning in their expenses (which generally yields faster results) and then switch to focusing on making more (which has unlimited upside)

But really though, I agree with the majority of what you said