Most properties will have reserves--a minimum bid necessary to buy the property. Sometimes these reserves are made public; sometimes they're not. There is such a thing as an absolute auction--no reserve--but even then the properties won't go for $1.00. Sure, they'll start out there. Then they'll quickly rise.
It varies, of course, but between the reserves and the bidding process, many/most properties that are sold get sold for 75%-95% of what they'd sell for if a Realtor had listed the property. Then you factor in the buyer's premium (typically 10%), consider that auction properties are sold in "as is" condition (so factor in another 1%-5% for paint, carpet, or more substantive repairs), the quick closing required for most auction properties, and so on, and what it comes down to is that finding a bargain at an auction is far more difficult than you'd imagine.