Blockchain technology provides the opportunity for several significant improvements in online marketplaces, especially online marketplaces dealing with virtual goods such as in the online gaming industry.

1. Greatly reduced transaction costs.
Dealing with fiat currencies, credit cards, etc, is very expensive. Whether the customer sees that cost directly, or experiences it indirectly in the form of increased prices, it adds friction and loss to the system.
2. Opportunity for peer-to-peer transactions without fraud
Purchasing virtual goods from a reputable website has always been relatively easy. Peer-to-peer transactions, however, has been difficult and fraught with danger. If a player wants to purchase an account, character, or virtual item from another player, preventing fraud is extremely difficult. Traditionally, online marketplaces had to act as a mediator and escrow, another difficult and expensive process when dealing entirely with virtual property and individuals over the internet. By recording ownership and transactions on the blockchain, fraud becomes nearly impossible.
3. Many individuals live in countries where buying things online at all is very difficult. For them, it will still somewhat difficult to get fiat money into a cryptocurrency but, once that's accomplished, individuals can exchange them for any cryptocurrency they need and buy and sell property online safely and cheaply. They can even start by earning cryptocurrency and operating entirely without fiat for those kinds of transactions.