One who profits from eBay, say

RESELLER

Think of someone who buys low and sells high online for extra cash.

This clue hints at someone who buys items (often at a low price) and sells them again for a profit, which is exactly what a "reseller" does. The mention of eBay is a nod to online marketplaces where this practice is common—it’s not about eBay itself but the type of person who uses platforms like it to flip goods. The word "profits" directly ties to the idea of making money from reselling, making the answer straightforward once you think about the role.