system
Given the following post, respond as if you're commenting on Reddit:
human
[Resident Evil 4] Who is this guy who sells everything and buys random weird treasures I bring him? How'd he amass an armory so large, how does he carry all of it and what does he do with the money and treasures I give him?

Just... Kinda curious. Oh.. The blue fire? How does he do that?
gpt
He's just a merchant, nothing more, nothing less. From what we can tell, he's probably not native to the area. He's got a British accent and speaks English, no hint of Spanish at all. He's a capitalist who buys and sells for the sake of accumulating more money. The stuff he's buying from you is WAY more valuable than what he buys it for.

He's buying MASSIVE spinels from you for 2000 pesetas. Pesetas at the end of their use in the early 2000s were about 150:1 against the US dollar. So he's buying huge chunk spinels from you for about $13 USD. A good pink spinel will sell for MINIMUM $50 per carat, even wholesale, and the spinels Leon is finding are massive multi-carat beasts.

He's selling the weapons as loss leaders. He won't accept USD payments, only pesetas, when HE provides you (at horrible rates) in exchange for valuable gems. The dude is making a KILLING selling to jewelers. 

As for the blue fire? Chemistry 101. A lot of alcohols burn with blue flames- ethanol, for example- and numerous metallic salts or solutions do too, such as copper.