The cheapest way to cover a popcorn ceiling is to scrape off the popcorn, then patch and paint the ceiling.

The cheapest way to cover a popcorn ceiling is to buy a can of spray insulation and do it yourself. First, remove any loose paint or debris from the ceiling. Then, spray the insulation onto the ceiling in even strokes and let it dry. You may need to apply more than one coat for complete coverage. Once the insulation is dry, you can paint over it with whatever color you choose.