I agree with everything that everyone has said so far. (Can this be possible?)
I've seen several -- but only several -- vintage '30s suits that were made by the finest U.S. tailors of that time. The fabrics compared well to the best Piana wools of today. We almost never see the best vintage menswear because there was so little of it made, and even less survives.
About 10 years ago, I went to many estate sales in the L.A./Pasadena area. I had three pieces of luck that will never be repeated: I found in the closet of a doctor's home a three-piece double-breasted suit made by "Sy Devore" of Las Vegas in 1951 for ... Dean Martin. That's right: custom made for Dean Martin just when his film career was taking off. The suit was amazing. It was a slightly trimmer, more streamlined version of the early '40s silhouette: the lapels were still wide, but somehow more ... Italian.
Also hanging in that cramped closet -- along with tons of awful polyester -- was a light grey flannel, single-breasted, peak lapel suit custom-made by the Warner Bros. wardrobe dept. in 1957 for ... Roger Moore. (He must have been very young at the time, and tall too: the suit was a 42 L.) Now, you'd think that a late '50s suit would have a boxy cut and thinnish lapels. Not this one! It looked like something Carey Grant would have worn in an early '40s film. The lightweight flannel was the finest I've ever felt: supremely soft and drapey. And the tailoring was superb. The true hallmark of a great tailor is the way he makes trousers. The pleated trousers on this suit were cut, assembled and darted in such a fluid way that they hid human defects and accentuated nature's gifts.
When I moved to Chile, I sold the Roger Moore suit to Art Fawcett. I ended up selling the Dean Martin suit to a TV sitcom writer. Things come, things go ...
One more find: a swallowtail coat custom-made in London in 1913 for a pre-presidential Herbert Hoover, the very year he entered public service by promoting commerce between the U.S. and Britain. The coat was in perfect condition: it looked new. I was struck at the fineness of the thick fabric's quality: a black cheviot wool that's just beautiful. The entire lining is pure silk. The tailoring isn't rigid, it molds to the body while paradoxically giving it room to move (and keeping hidden the way that was achieved).
Believe it or not, I found this coat (and one of Hoover's hats, a British flat-topped bowler similar to Churchill's) at an estate sale in, of all places, South Pasadena. Turns out that one of Herbert Hoover's sons settled there; when that son died in the 1960s, his family held an estate sale and a neighbor bought a lot of clothes -- including some belonging to the ex-president. It was at this neighbor's own estate sale that I found Hoover's hat and coat. I also bought a tailcoat and a pair of linen golf knickers belonging to his son.
Now that coat I still have! I sold the hat and the other clothes.