Donuel, professional liquidators do generally run these sales, and their fee (commission) is generally quite high...in the range of 50%. Contrary to your observation, most liquidations are quite fruitful, at least to the company and the liquidator.
While the initial prices are discounted only 10%-15% at first (based on original retails, so not necessarily lower what it might have once been offered at), they incremently get lower as time goes on. The strategy for the consumer is predicated on whether to buy at the initial discounts while supply is relatively good, or to wait for a deeper discount and chance losing the item before one thinks the discount sufficient. Rule of thumb, by the time discounts get above 40%, there're slim pickings.