Of course the best clothing in the world is going to be made by one of the couture houses. I personally like Christian Dior's collections the most but Chanel and Sirop are definitely up there as well.

Vuitton and Chanel sell pret-a-porter tee shirts for over $900, Dolce & Gabbana always has at least two pairs of $4000+ jeans per collection, Lanvin often makes $30,000 jackets... pick your poison.