system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are certain items (like cars and mattresses) sold with such flexible pricing but other items are not?

I just bought a mattress and was able to negotiate and bring down the price on every element of the deal. But, why are certain items sold this way while other things have much more rigid pricing?

Are there specific market factors? Historical reasoning? Or is it just an anomaly?

And, would it benefit or hurt consumers if more or less items were sold this way?
gpt
Some would argue that all items have negotiable prices.  As an example, you can totally negotiate with Walmart and end up paying a lower price.

The difference is that a car or mattress is a large dollar value purchase that is not made very often.  So you (the consumer) has fairly large power because once you've bought you are unlikely to buy another for a long time.  If you are just buying bread, well you buy bread all the time as does virtually everyone on the planet.  So your power as a consumer is virtually zero.