Depends hugely.
My mother once told me that her rule of thumb for an investment piece (winter coat that is going to last years, black tie dress that can go anywhere and will never date etc) is that one week's wages is an entirely reasonable sum, if you can afford it. They must never date and be of top quality. Her winter coat is from the 70s, and is timeless and elegant and still looks as good as new.
My godmother has a black tie (long black sheath dress with beautiful embroidery) from the 50s that still looks stunning, and I've worn a number of times. Her mother thought she was insane to spend two weeks' salary on it, but her grandmother had the same attitude as my mother and encouraged her, and it has certainly paid off - all the younger generation have worn it and it still makes me look and feel amazing.
It all comes down to can you afford it, and if yes, will it last, and be worn again and again.
My clothes generally come from charity shops or the sales (and I don't buy clothes often). But I do have a few very expensive clothes, which when I wear I feel amazing and always am complimented - not least because I feel confident, so stand up straighter, am better company etc...
However, the majority of clothes nowadays (and I'm not as old as that just made me sound!!) I don't think are worth the money. The quality has gone down. It is harder to find good silk blouses etc. The pattern is disrupted at the seam and doesn't match up, to save on material.
So to end the epistle, yes I have spent that much money. But only on clothing I think is worth it, and only occasionally - I don't need ten investment black tie dresses, or ten investment winter coats. And most clothing I think is overpriced tat wherever it is.