There is nothing that says the same isn't true of expensive clothing (and for that matter, online services). They may still cut the costs in the most unethical manner possible. They'll just have a higher profit margin at the same time.
If a no name brand starts to make quality t-shirts, no one will know about it, and no shops will stock it, because the margins will be too low and the marketing will have too little budget.
If it takes $1 to make a shitty $15 shirt, and $15 to make a proper shirt, what will you charge for the proper quality shirt? How will you market it?
The end result is that they're marketed as super high quality only available for the sort of person that can afford to spend $100 on a basic shirt, just to compensate for the decreased margin and decreased demand.
The solution would have to be that these kinds of brands need to be ran by charities, with such low margins that no one gets rich of it. You need someone to splurge a couple million to buy a factory in India, and then increase wages and conditions until you make 0 profit.
Is it true that the only way to run capitalism humanely, is to have capitalists surrender their money?
If we would force India to also enforce those conditions, all we would do is make their factories unattractive, and business would move to another country.
Solving that, would perhaps require legislation to ban clothing (et al.) companies from using offshore factories that are not under close scrutiny of our own government. But perhaps that will just make our brands like H&M unattractive to more liberal countries like the U.S.