I mean, I'm an American. I have a pro-American sentiment when it comes to food and drink.
I also happen to have an anti-overpriced-crap sentiment when it comes to the things I eat and drink.
In my area, a Quarter Pounder with Cheese is $10.50. Now, I may not compare exact apples-to-apples here, but let's go for it.
From my local supermarket, I can get 20 1/4lb. patties for $25 - that's the premade patties, not from the butcher section. That means not only can I decide how well-done I like my burger, I can season it as I choose. And I have confidence in my local supermarket that when they put on the side of the box "Ingredients:80% Lean, 20% Fat Ground Beef", they mean it. That makes each patty $1.25.
Now, if I want to buy the exact same ground beef, but not formed in patties, that's $3.25/lb (usually in 2-3 lb. packs, but I can ask the butcher and get a custom size) - so now we're down to $0.81 for the patty.
The rolls, I can get store brand. 8 for $1.50. That's $0.19 cents a roll. That means that if I buy my own ground beef, I've now spent exactly $1 on a quarter pound burger. So let's talk toppings.
The cheese first - one slice of American on theirs; I would go a different way, but stick to them. Springing for a little extra, $3.59 a pack for Borden Melts cheese, 16 slices. $0.22 per slice. Our burger is now at $1.22 COGS, and I have the makings for 7 more in buns and probably that in beef, plus I could make each burger with 2 slices of cheese, so each burger is $1.44 so far.
Onions, I can get for $1.50/lb (or less!), and each onion is less than that. But I definitely have enough to do a burger and meal plan - let's say an ounce, about $0.10. Mustard, I'm not going to factor in the cost, because it's so little as to be a joke. Buying a jar of good mustard can last you a year or more. Ketchup I'll say the same for. It can last a long time and the amount per burger is negligible. So let's be generous and say $0.10 each. Pickles can be more expensive if you get good ones, but store brand we're talking $0.16 per ounce (with brine), and you're not putting on a full ounce of pickle. So in toppings, we're adding ~$0.50 value.
Total cost of the burger is around $2.00 at retail, not at scale; about $3 if you want premade patties. Sure, there are costs to be amortized like rent and tax and cooking - and the biggest cost, labor. But each individual burger shouldn't be socked with an 80+% markup from COGS, and taste worse than the home-made version.
Why should I buy from McDonald's ever again?