Okay, here's the situation: When a middle-class stay at home mom says this she's just being lazy and using excuses.

But there are people who actually are hindered by the fact that eating healthy is a very significant investment, possibly one that's too costly to afford, compared to eating unhealthily.

Frequently we consider expense as just the price tag, but it is actually far more. Travel to and from the store, the time out of our day to educate ourselves about nutrition then the time to shop for, prepare, and eat healthy meals, and the cost of not being able to buy in bulk.

I (and many/most others here) are fortunate we have free time in our day that we could spend on meal prep if we wanted to. We also ahve the resources to teach ourselves about nutrition.

On top of that, when we do decide on a healthy meal, most of us can use our own car or convenient public transport to reach a grocery store that is well-stocked with healthy food for that meal we've planned.

This is not the case for many truly poverty-stricken people around the world and even here in America. Frequently you'll have single parent households where the parent is working multiple jobs and what little time (s)he does have probably must be spent looking after the home and children. (Arguably being healthy is part of that, but when the choice is "find a way for Jimmy to get his 5 fruits/veg a day" or "See the principal for the mandatory meeting about Jimmy's behavioural problems or he gets expelled" one must prioritize.)

Many poverty-stricken households exist in food deserts, areas with limited or no access to fresh produce and other healthy, affordable options. While there may be stores further away with better options that would require travel, often on public transport meaning that frozen or refrigerated food is likely out of the question since you won't be able to get it home and refrigerated in a safe amount of time. That's if public transportation is available at all. I live in a rural area where most of the county is under the poverty line. A few months ago I picked up a 68 year old man who was walking in the rain, making an 11 mile trek to our nearest city to have lunch at the senior center. To people like him, healthy food is a massive investment, regardless of how close the price tag numbers are to the processed junk.

TL;DR: Most of the people who say eating healthy is too expensive are liars who are looking for an excuse. But please recognize that food security and affordable healthy options is a significant hurdle to nutrition for many people and don't scoff at everyone who says they find it too expensive to eat healthy.