Are lockers as expensive as I see on the TV shows?

They can be, but you can buy lockers from $1 to $x,000.  An educated "guess" says depending on your location the average price is $100 to $300.

There is no way to predict what a unit is going to sell for these days, there are too many variables like how many people are in attendance and the quality of the merchandise that is visible from the door.

Storage units used to sell at a reasonable prices and everyone made money. Prices have definitely risen since the storage auction reality shows came out, although it is still possible to get a good deal if you're patient. At some storage auctions, the lockers do sell at prices similar to what you see on TV. This is primarily due to new inexperienced bidders running the prices up.