The price of some electronics may be flat, but alot of it is actually going up. People are still paying for stuff like smart watches and smart phones and so on, though it's mostly a dwindling percentage of the population.
Also, it's been processed foods that have gone up in price the most. However, processed foods account for about 60-80 percent of the average American's diet. Add in foods like meat or eggs, that have alot of hidden "manufacturing", and the percentage goes even higher. Foods like beans, grains, or vegetables really haven't changed as dramatically.
I buy the Basmati rice in the 10 lb bags and the cost of rice has exactly doubled in the last 15 years. I don't believe it was available to buy back in the 80's so I can't much compare that far back.
Things like cans of soup - which people buy constantly, I have many casserole recipes that call for canned soup - boxed macaroni and cheese, jars of honey etc really have increased dramatically.
The problem many, if not most, home cooks face is the problem of the cost of going completely from scratch (making your own cream of mushroom etc)
When times are going good in life people can do that, I was pulling in around 5,000 a month in '92, a number that drastically dropped when I got a real job (I decided I wanted days off and a normal work schedule more than money, as opposed to my own business, not that such a thing actually ever occurs anywhere I have learned... Lol)
So life itself changes and there's times your dependent upon the canned goods as opposed to all fresh ingredients. (I mix it up so you can't tell as much...)
I'd say the percentage of people depending today upon canned goods - especially in the days of food TV - as opposed to fresh is telling as to how much money people have.
Some things are far less expensive to make from scratch - I still make homemade breads as much as physically possible because the difference in cost is dollars, not pennies. Same with pastas. I just make it...
But the more processed food is, the cheaper it often costs unless you're buying beans and rice - which I use plenty of... So the more of processed food people are buying, I think the less money they have.