Sale shoppers are the dung beetles of the retail world. They are the maggots feeding on the carrion merchandise. They are necessary. Without them, the dead items of seasons past would linger for years, fingered and handled until they are stock-lossed and tossed.
They are necessary, yes, and they also bring a certain repulsion with them. I and others are disgusted by their heckling over prices, nick-picking at the condition of merch, paranoid receipt checking.
These are all normal shopping habits, but during a sale, they are boiled down into a frenzy of impulse, desire, thrift, and remorse. Most of us have been this shopper at one time or another; do not let it become your main shopping mode. Keep your dignity and avoid the reputation (which you will get behind your back) of Clearance Whore.