Officially, Paris is not the most expensive city in the world. But it seems like it is, bc they have almost all the high quality designer brands. I will tell you where you can find the best clothing pieces in Paris.
If you can schedule your trip to Paris during the bi-annual sales periods in January/February and June/July you gonna see almost everywhere discounts. And when they gonna do discounts they gonna do it right. Not like just 10%off. During the bi-annual sales periods in January/February and June/July you can find really nice pieces from the best designer for up to 70%.
The best place to find your best pieces is Gallery Lafayette. It’s one of the most popular Shopping centre. There are almost all the luxury Brands.
If you don’t exactly know what you want to buy you should go the Gallery Lafayette. But if want a special shirt from Balmain, i think it’s better to get it in the official store outside the shopping centre.
So have fun with shopping!!