Extracanonical subject (Unique game aspects not part of story canon)
The Degeneration Merchant is an entirely different character from the Resident Evil 4Merchant. He doesn't say as much as the Merchant from Resident Evil 4 and sports military attire similar to some of the special force soldiers in the game. He wears a gas mask of sorts however.
The RE4 system returned in Degeneration, though is much simpler. Resident Evil 4: Mobile Edition has another "merchant" version whereby the player is taken to a pre-game lobby where they can sell and upgrade items; it is therefore more comparable with the Resident Evil 5 system.