One of the biggest mistakes store owners make at the end of a going out of business sale is getting rid of the last remaining inventory. It could be they believe everything will sell at 50% off. You will sell a lot of that price, but slowly the sales will trickle down to nothing.
Many owners have a hard time selling items below cost. This is understandable while running your business, but at the end of a store closing sale, costs should not matter. The only thing that matters is how much you can get for it.
Most of the time after 50% off, I will go 70% off for a week and a few days at 80% off. During the 80% off, I will take offers on slow-moving sections and sell them in bulk. Most stores are talking about thousands of dollars they can put in their pocket while minimizing expenses. Otherwise, there will be a point of time, your revenues will be less than your expenses.
I have seen stores keeping their doors open for less than $100 a day in sales because they would not take additional markdowns or sell the sections in bulk.