StockX is an online marketplace for buying and selling high-demand sneakers, streetwear and other goods. It has raised $6 million in funding from investors like Mark Wahlberg and Eminem. The company profits from transaction fees that start at 9.5-14.9% but decrease as users make more sales. StockX aims to bring transparency and authentication to the over $1 billion sneaker resale market, where there was previously no safe way for legitimate online transactions.