I'm sorry, but the notion of major markups is a bit of a myth.
The reason some stuff is so cheap is because it's rubbish. It's mass produced by machines, and where there is any human involvement, they are on piece work. Hence the reason most of that sort of donkey work is done in Asia.
The best items have to source the best materials. They can't buy in huge quantities so they pay over the odds for raw material.
The best items are made individually, even when they are mass produced. Women's shoes, for example. If too many of the same style are made, then they don't sell. Simply because most women want something different. Men, on the other hand, prefer standard. Standard style, standard colour, standard material. Hence, mass produced so cheap. And rubbish.
I wear only the best quality shoes, simply because my feet are so important. But I do have to pay, £60+ a time. However, even the very best quality men's shoe is a fraction of a high quality women's shoe. Hence an equivalent women's shoe is 4 times as much. My wife wears the same men's shoes as me. No problem. If I walked down the street wearing women's shoes, I'd probably be beaten up.
It's a bit complicated, but there are essentially two factors that make the biggest companies successful. Franchising and outside sourcing.
Franchising is just a scam, where someone makes a name for themselves, forms a company of that name, based in some low tax haven place, such as some offshore island, which copyrights it. Then, the original company or person pays the company which owns the name, an enormous fee to use it. They own the company. They own the name. But fee is tax deductable in most places. All large companys work that way. It's also common for the biggest names in entertainment. Musicians, actors and anyone like that.
Outside sourcing is a bit more complicated. You need leather to make your shoes. You find various places that produce it. You form a company to buy that leather. Your own company sells the leather to you at enormous profit. You claim tax relief. It's complicated because your sourcing company needs to work as an active unit, rather than the more direct scam of franchising. It is subject to fluctuation is supply and for financial reason, the owners can lose control.
Most retail stores, other than multinationals, make very small profits.