Hi Dante,
The value of a mattress purchase has many components (see post #46 here) and includes objective, subjective and even intangible factors that may be more or less important to different people. The quality/durability of a material is not subjective at all though and can be quantified to some degree based on the type of materials and the design of the mattress (see post #4 here about the factors involved in durability). The density of a foam is the single most important part of its durability and some foams and materials are objectively more durable (and usually more costly) than other materials.
A mattress is only as good as the quality of the materials inside it and higher quality materials in general are not only more costly but more durable. The problem is that most major manufacturers don’t disclose the quality of the materials in their mattress and if you are able to find out what they are (which normally takes a great deal of time and effort or in most cases sources of information that is not generally available to consumers) you will find that the quality of their materials in each price range is typically lower and less durable than similar mattresses made by smaller more independent brands. The very rare exceptions are really not worth the time and effort it takes to find them. Point 1 in other words is about quality.
Point 6 is very different and it is all about the suitability of a mattress which is partly objective and can be tested and partly subjective (like comfort). You can’t feel the quality of the materials in a showroom or know how a mattress may feel in a few years down the road once the foams and other materials start to soften or break down. In other words … lower quality materials can feel the same as higher quality materials … they just don’t stay that way as long. Point #6 is about the suitability of a mattress.
When you are buying a mattress … knowing the quality of the materials is one of the most important parts of making meaningful comparisons between mattresses and an important part of the value of a mattress but testing a mattress for it’s suitability (regardless of the quality of the materials) to make sure that the mattress you are considering is suitable for your specific needs and preferences is just as important even though they are two completely different things.
Phoenix