It is widely considered that buying a house at auction is cheaper than purchasing a property via an estate agent.
Often this is because auction houses will only accept properties if they're to be sold for less than they otherwise might have been, or because they've advised the seller to list their property's reserve price lower than the price they'd expect to sell for through an estate agent. Therefore, buyers do have the potential to buy a house for less than it may have normally been worth, or perhaps buy a bigger property for the price of a smaller one being sold traditionally.
As a buyer, you must be aware that not all auction houses are bargains though. And the ones that are bargains may not be as they seem on the surface. So do your homework, make sure you know what you're getting into before bidding, and never bid beyond your set budget.