Best congnac for around $40?
Again, there is no "best" -- it's up to each individual's palate. Ms. X may prefer ______, while Mr. Y may prefer ____________ over the other one.
That said, Maison Surrenne -- http://www.surrenne.com/ -- is a small producer, still family-owned, that makes outstanding Cognacs. The Maison Surrenne Ancienne Distillerie Petite Champagne Cognac carries a retail price of $32-35, and is MUCH better than anything from the major houses at that level.
Another delicious option is Cognac Tesseron -- http://www.cognactesseron.com/uk/index.html -- which starts out in the mid-$40s, and is also quite delicious.
Also truly superb are the Cognacs from Logis de la Mothe -- http://logisdelamothe.com/ -- which is another small producer that has been around for generations, and well worth looking for.
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One suggestion that has already been mentioned is Germain-Robin -- http://www.germain-robin.com/ -- a California Alambic brandy produced "in the style of" a fine Cognac. (Hubert Robin's family produced Cognac for generations, prior to finally selling their firm to Martell.) Truly excellent brandy. Their Alambic starts in the mid-$30s.