The Chafetz Chayim, in two contexts (Sefer Ha-mitzvot Ha-katzar, lo ta’aseh 40; Shemirat Ha-lashon, appendix, chapter 4), addresses the case of a groom or parents of a groom who pressure the bride’s parents to increase the dowry amount beyond the sum to which they had committed. In the view of the Chafetz Chayim, such pressuring violates the prohibition of “lo tachmod” (“Do not covet”), the final of the Ten Commandments. Since the groom asks for money that was not offered to him, he transgresses this prohibition, which forbids pressuring somebody to sell something in their possession which they do not wish to sell.
Rav Asher Weiss, while conceding that such conduct is improper, questions the application of “lo tachmod” to this context. The prohibition of “lo tachmod” is presented in the Ten Commandments as forbidding the coveting of another person’s actual possessions, not his money. The desire to legally obtain money is something perfectly natural and lies at the foundation of economic life. Of course, the Torah discourages obsessively preoccupying oneself with money and urges us to exercise moderation in our material pursuits. However, this ideal of materialistic moderation in no way precludes reasonable negotiation. Buyers and sellers are perfectly entitled to negotiate prices, and this applies to other financial arrangements, as well, including marriage (in societies where financial considerations are a major component of a couple’s agreement to marry). Certainly, trying to raise a price after an agreement has been reached is improper, but this does not transgress “lo tachmod,” which refers to the effort to obtain a particular object which another person owns. This prohibition, seemingly, applies only when one desires somebody else’s item, but not if he wants to extract money from that person and thus initiates a process of negotiations in an effort to reach a profitable agreement.
By the same token, Rav Weiss notes, the prohibition of “lo tachmod” does not apply to applying pressure on somebody to sell something which is readily available elsewhere. If a person does not desire a particular object, but rather a certain kind of object, and he pressures somebody who owns the item in question to sell it for a cheap price, this does not transgress the violation of “lo tachmod.” In this case, too, the individual seeks not a particular object which is under another person’s possession, but rather to save money on his purchase, which is a perfectly valid desire. As such, this does not entail a violation of “lo tachmod.”