"Au revoir, Monsieur Vente!"

Which is the punchline of an old joke, that goes like this:

An American visiting Paris, but without knowledge of the French language, was happy to spot a postage stamp dealer's shop. Remembering that he wanted to buy his friend back home some souvenirs of his trip, he went in and bought a few high-value US postage stamps on display; presumably garnered from packages that had been sent over to Paris. He carefully wrote down the name of the shop lest his friend back home wish to inquire as to other stamps which the merchant might stock.

When he returned home, he excitedly told his friend about the discovery. "It's a partnership," he exclaimed, "Timbres Achat et Vente."

His friend shook his head at this useless information. "That just means 'Postage Stamps Bought and Sold."

"Oh," replied his travelling friend, "So that's why the guy looked at so strangely when I said, (YOUR BIG LINE) -
'Au revoir, Monsieur Vente!"