Where is the Value? (Proverbs 20:14)

Have you ever downplayed the value of something just so you can get it cheaper?

"It is worthless, it is worthless! says the buyer; but when he goes his way, then he boasts [about his bargain]." Proverbs 20:14, Amplified

The Bible seems to make no indication that this is a wrong practice to take part in. The buyer, himself, sees the value in an item and downplays it to the owner. But I do have to say I do see that the buyer goes away boasting about his bargain. In other words, he tells everybody how he got over on a poor schmuck. To see the value in something and want it for cheaper is not a bad thing in and of itself. I am a collector of comic books and I always peruse garage sales looking for these little gems hoping that no one sees their value. It is an exciting feeling to get your hands on that hidden treasure, on that found thing. This is exactly why people want to brag about the bargain.

But I do not see this here in the verse. It seems that the language implies the buyer is telling the seller that his wares a no good. He wants a batter deal despite the livelihood of the seller. He is a miser who wants to press the value out of every penny in order to get over on everybody. His boasting may cause others to go to the same seller and get the same deal, thus stripping the seller of most of his profits.