Naught - Bad, worthless 2-Kings 2:19.

It is naught, it is naught, saith the buyer - How apt are men to decry the goods they wish to purchase, in order that they may get them at a cheaper rate; and, when they have made their bargain and carried it off, boast to others at how much less than its value they have obtained it! Are such honest men? Is such knavery actionable? Can such be punished only in another world? St. Augustine tells us a pleasant story on this subject: A certain mountebank published, in the full theater, that at the next entertainment he would show to every man present what was in his heart. The time came, and the concourse was immense; all waited, with deathlike silence, to hear what he would say to eaeh. He stood up, and in a single sentence redeemed his pledge: -
Vili vultis Emere, et Caro Vendere.
You all wish to Buy Cheap, and Sell Dear."
He was applauded; for every one felt it to be a description of his own heart, and was satisfied that all others were similar. "In quo dicto levissimi scenici omnes tamen conscientias invenerunt suas.' - De Trinitate, lib. xiii., c. 3; Oper. vol. vii., col. 930.

It is naught, it is naught, saith the buyer,.... When he comes to the shop of the seller, or to market to buy goods, he undervalues them, says they are not so good as they should be, nor so cheap as he can buy them at;
but when he is gone his way, then he boasteth; after he has brought the seller to as low a price as he can, and has bought the goods, and gone away with them, and got home among his friends; then he boasts what a bargain he has bought, how good the commodity is, how he has been too many for the seller, and has outwitted him; and so glories in his frauds and tricks, and rejoices in his boasting, and all such rejoicing is evil, James 4:16. Jarchi applies this to a man that is a hard student in the law, and through much difficulty gets the knowledge of it, when he is ready to pronounce himself unhappy; but when he is got full fraught with wisdom, then he rejoices at it, and glories in it.

Men use arts to get a good bargain, and to buy cheap; whereas a man ought to be ashamed of a fraud and a lie.

when . . . his way--implying that he goes about boasting of his bargains.

The following group has its natural limit at the new point of departure at Proverbs 20:20, and is internally connected in a diversity of ways.
14 "Bad, bad!" saith the buyer;
And going his way, he boasteth then.
Luther otherwise:
"Bad, bad!" saith one if he hath it;
But when it is gone, then he boasteth of it.
This rendering has many supporters. Geier cites the words of the Latin poet:
"Omne bonum praesens minus est, sperata videntur Magna."
Schultens quotes the proverbs τὸ παρὸν βαρύ and Praesentia laudato, for with Luther he refers ואזל לו to the present possession (אזל, as 1-Samuel 9:7 = (Arab.) zâl, to cease, to be lost), and translates: at dilapsum sibi, tum demum pro splendido celebrat. But by this the Hithpa. does not receive its full meaning; and to extract from הקּונה the idea to which ואזל לו refers, if not unnecessary, is certainly worthless. Hakkoneh may also certainly mean the possessor, but the possessor by acquisition (lxx and the Venet. ὁ κτώμενος); for the most part it signifies the possessor by purchase, the buyer (Jerome, emptor), as correlate of מכר, Isaiah 24:2; Ezekiel 4:12. It is customary for the buyer to undervalue that which he seeks to purchase, so as to obtain it as cheaply as possible; afterwards he boasts that he has bought that which is good, and yet so cheap. That is an every-day experience; but the proverb indirectly warns against conventional lying, and shows that one should not be startled and deceived thereby. The subject to ואזל לו is thus the buyer; אזל with לו denotes, more definitely even than הלך לו, going from thence, s'en aller. Syntactically, the punctuation ואזל לו [and he takes himself off] (perf. hypoth., Ewald, 357a) would have been near (Jerome: et cum recesserit); but yet it is not necessary, with Hitzig, thus to correct it. The poet means to say: making himself off, he then boasts. We cannot in German place the "alsdann" [then] as the אז here, and as also, e.g., at 1-Samuel 20:12; but Theodotion, in good Greek: καὶ πορευθεὶς τότε καυχήσεται. We may write ואזל לו with Mercha on the antepenult, on which the accent is thrown back, cf. חונן, Proverbs 19:17, but not לּו; for the rule for Dagesh does not here, with the retrogression of the tone, come into application, as, e.g., in אוכל לּחמי, Psalm 41:10. Singularly the Syr. and Targ. do not read רע רע, but רע לרע, and couple Proverbs 20:15 with 14. In the lxx, Proverbs 20:14-19 are wanting.