Hi johnoliver,
It certainly never hurts to try or ask “is this your best price?” or “is there anything else you can include in the purchase?” but many of the better retailers or manufacturers already list their lowest prices and they know that they already compare well with the “after sales and negotiated prices” of other similar mainstream mattresses so that the price a customer pays doesn’t depend on “bargaining skills” and the “value” of their mattresses don’t depend on perceptions based on the percentage of a discount off a “fake retail price” that nobody ever pays anyway.
The most effective “bargaining” tool is to make “apples to apples” comparisons with other mattresses that uses the same type and quality of materials and components in the same or a very similar design and layer thicknesses and to ask them if they can come any closer to another mattress that is very similar that is also available for you to purchase. There is more about the most important parts of the “value” of a mattress in post #13 here and there is more about “negotiating” prices in post #6 here that may be helpful.
Phoenix