When sales were originally introduced, it was for the reason of clearing out a shops old stock to make room for the new.  They could have just thrown out the old stock , which of course would not be profitable.  Even with 50% or what ever percentage, the shop is still making a profit. It is a pity that there is not a law, which compels shops to state the price they paid for the item, to compare their mark up to the price they are selling it to the public.  
Now sales are just an excuse to get you into the store, with the hope you will buy items that are not in the sale.
In past years it has been known for certain stores to buy in seconds just for the sale.
If you like shopping and do not mind crowds, then go to the sales, but not every thing you buy will be a bargain.