An average wage for a factory worker in Bangladesh seems about $0.33 USD; in Cambodia it's $0.85 USD; other countries are somewhere in between.
I don't know how many clothes a single worker can make, but let's be extremely conservative and say it's two pieces of clothing per 10-hour workday. So that's between $1.65 an $4.25 in wages for a single piece of clothing. I suspect it's actually much much less (but can't find any resources on this at a moment's notice). Even this amount is ... not that much. A 50% or even 100% increase would make a huge difference in people's lives, while having a fairly minor impact on this end.
I grew up fairly poor and for the first 25 years or so I basically never had enough money for anything, so I understand that "a few € more or less, who even notices?-attitude that someone more well-off/middle-class might say is actually not so easy. I know from experience that those "few euro" actually can be quite significant. This is one reason Primark is so popular in the first place.
But still: the difference is stark, and there is little doubt in my mind what is clearly The Right Thing™ to do is here.
I understand that companies want to keep costs down, and that's perfectly reasonably, but this is just ridiculous and extreme. In many cases workers barely have enough money to buy food. And for what? So it's €1 or €2 cheaper? I find it so hard to believe that, as I said in the first line, I must not understand the economics of this somehow. Or maybe I do and people involved in this are just ... ugh...