The issue is that even if you pay well above $50 there's no guarantee that the t-shirt will actually be any good after 10 washes. I have two t-shirts from 15 years ago that are still going strong. Whatever I buy these days becomes 'home' t-shirt fairly quickly.
[0] back of napkin math - i might be able to find a decent knit cotton with some veneer of ethical sourcing at a rock-bottom price of $10-12 per yard (in practice F to doubt). Assuming a pittance for the thread (and ignoring the upstart costs for acquiring a sewing machine), I would peg my skillset at a value of $35-50 per hour given my experience based on the rates of similarly skilled artisans in the US.