Hi Bun,
It would depend on which store you are talking about. Many of the better retailers or manufacturers list their best prices on an every day basis and don’t need sales to have better value than the “best” sale prices or “negotiated” prices at more mainstream stores. Others may have have a series of rotating sales which are usually just part of their regular selling price and are for perception and marketing only and others may artificially raise their prices so they have room to give something back with so called “negotiations” which makes some customers feel like they have received some kind of “special deal”.
You can read more about “fake sale prices” in post #5 here and more about negotiating in post #6 here.
It certainly never hurts to ask if they ever have sales or if a price they charge is their 'best price" or if they can add any bonuses to the purchase but again there are many better manufacturers or retailers that give every customer their best possible price without the customer having to ask or negotiate at all so with these they already know that they are in a better value range than the “after sale and negotiation” prices of their competition with any “apples to apples” comparisons with other similar mattresses and you may find that they would rather lose the sale than provide a further discount on top of an already great price.
In general … if you see “huge sales” on a regular basis then I would treat this as a caution and even the sale prices are typically inflated.
Phoenix