Luxury brands usually produce in the same places as fast fashion, the only difference is their margin when selling. If you want it sustainable and with fair working conditions, it’s also cost about the same, but you’d have to look for it (and probably will only find a few products of luxury brands)
That’s why I have my own definition if “luxury”: Sustainable materials, humane working conditions, timeless style, long lasting construction etc.
I have to look for it, especially since I buy second hand, but not very often because of, well, whatever I buy is timeless and long lasting. No need for frequent replacement.