SQL Server Isolation level real world example

Let's say we need to develop a bidding application such as one in eBay. We don't want one user's bidding to block another user's bidding, which will result in slow response. Also, when I place a bid based on the highest price I see, I don't want to arrive at the end with the app saying that sorry, the highest price was no longer the same; while I am placing the bid someone has pushed the price higher.Let's say we need to develop a bidding applicat