Speaking truthfully protects against death, as the Gemara recounts (Sanhedrin 97a) about a place called “Kushta” (“Truth,” in Aramaic). Everyone in that place was careful to speak only the truth and not one of them ever died prematurely. Our Sages said (ibid. 92a) that one who lies is considered an idolater. There are some people who have so trained their tongues to lie that lying feels perfectly permitted, and so they lie needlessly, telling tall tales for no reason. To them, anyone who lies to gain profit is “Hard-working” and “seasoned.” In fact, they maintain that if you don’t lie about your merchandise, you can’t make a profit. But that is absolutely not true, as we see in this Midrash (Shochar Tov, Tehillim 7): When Noach was entering the Ark, “Falsehood” also wanted to enter. Noach told Falsehood that only couples are allowed to enter the Ark. So Falsehood went looking for a mate and found “Decay.” He promised her that whatever he gains he will give her. And since then, whatever is gained through falsehood is lost to decay.
And even if the Yetzer Ha’ra shows someone that he will earn grait profit through lies, there is no doubt that in the end he will lose it all or it will be riches hoarded by their owner to his misfortune (Koheles 5:12) in this world and in the World to Come.