There are a lot of mattress stores because they are inexpensive to open, the market is huge (every domicile probably has at least one mattress) and the profits on a mattress can be ridiculous.
Mattress stores have a fairly low overhead. Display mattresses are typically free or at a very low cost from the manufacturers and you can sell them when you are done with them. Staff is either commissioned or paid about $14/hr with bonuses. Commission reps get either $9/hr or their commission. An average rep was probably taking home $1000/week, top performing reps double that.
The store is probably at least Net30 billing from the manufacturer, so you have 30 days to sell the mattress before you have to pay for it. If you are turning over mattresses fast enough, the capital outlay for product is minimal.
2Bits is right about the mark-up in mattresses. A premium queen sized mattress that sold new for $3500 might carry a cost of about $2000. Sleep on that mattress and return it one night later under the 120 night return policy and it is sanitized and put into clearance. That mattress that was in the inventory as new with a cost of $2000 will come back out to the store as clearance item with a cost of just $699 and probably be marked in the store for $1750 (half of list). And on a slow day, $800 could take it home.
So the real mark-up on that premium mattress is what, at least 500%?
There is almost zero consumer transparency when it comes to pricing. Labels are easy to change for each retailer so that the consumer can’t really compare mattresses by name. Maybe you buy the Acme Sleep Well for your store. My chain has 50 stores so I pay for them to sew in a label that says Acme Sleepy Well. Features can be customized for every retailer as well. “Oh, they have 300 coils in their Acme Sleep Well Mattress? We’ll have Acme put 350 coils in the Sleep Well they ship us.” Unless you know how to dig into the mattresses and the manufacturers, the average consumer has no way to compare mattress prices.
I am out of the business now, but I advise everyone to pay no attention to anything but the list prices and after you find what you want, offer to buy today if they take 50% off the entire set-up: mattress, foundation, pillows, everything. If they will do 40% you are in pretty good shape, too. Some stores will negotiate, some won’t. At the firm that I worked at, any sale where we made a dollar or so in profit was a good sale.