As part of the Season of the Malignant, AKA Diablo 4 Season 1, players can choose to purchase a season blessing. These are boosts that come in urns, like the Urn of Aggression, which increases xp earned from kills, and the Urn of Malignance, which increases the rate of Malignant Heart drops. Then there's the Urn of Bargaining, which is supposed to increase the amount of gold you earn by selling gear to vendors. And that's where the problem comes in.
You want to be careful not to waste gold in Diablo 4, as it becomes more valuable later on when you'll need to pay the Occultist to shift aspects from one piece of legendary gear to another. That's the source of the first problem with the Urn of Bargaining, which is that it increases the cost of vendor services. You'll end up spending more gold on enchantments at the Occultist, and on repairs at the Blacksmith, and on every other service offered by Sanctuary's shopkeepers.
What's more, as several players have reported on the Diablo 4 forums, the Urn of Bargaining doesn't always increase the amount of gold you earn from selling items. While the increase to vendor service costs seems consistent, the absence of an increase to sale prices seems sporadic, however, with some players reporting this bug but not others. Whatever the case, it's definitely not worth picking the Urn of Bargaining as your season blessing at the moment.
Season blessings, by the way, are earned by spending the Smoldering Ashes currency, which is earned by leveling up the battle pass with Favor. I'll let you know when I figure out how Malfeasance Tokens factor into it, and how this is affecting the Affliction Coin economy.