Hi AndrewR,
When you are considering latex then you are looking at a very durable material no matter what the type or blend. While it’s normally true that Dunlop that has a lower amount of natural rubber would tend to be less durable than 100% natural Dunlop … some of the testing that Mountaintop has done on their synthetic latex (which is what is used in the Casper) is promising and indicates that it’s a very durable material (although it still has a different “feel” than natural Dunlop) so I will keep an open mind to see how it plays out over the coming years. 4 lb memory foam in general will also tend to be less durable and less costly than higher density memory foam but it may also have properties that some people prefer compared to higher density memory foam (see post #9 here and post #8 here about some of the differences between different types of memory foam) so this would also be a personal preference issue.
These are all “preference” or “best judgement” decisions that each person needs to answer for themselves based on the parts of their personal value equation that are most important to them. While you can assess the quality of different materials based on their specs … you can’t really assess how a mattress will feel or perform to you in terms of PPP based on specs (either yours or the mattress) so when you are looking at online choices (and comparing online with online instead of online vs local) then the confidence you have that a mattress is a good match for you will depend on your local testing, your general familiarity with the overall properties of different materials (even if it’s not the same design of the mattress you are considering) and your conversations with each online retailer or manufacturer. The options you have to choose between a range of mattresses or customize a mattress before and after a purchase and the exchange or return policies can also play a significant role in the “value” of your purchase as well. Don’t forget that the people who don’t exchange or return a mattress will be paying for the ones that do (free return policies are built into the cost of a mattress) and that return rates will generally be higher with “one size fits all” mattresses than with mattresses where you have more options available.
While there are better “value” mattresses based on the cost of the raw materials inside them in the same budget range (such as mattresses that use 8" or 9" of synthetic latex vs 1.5" of synthetic latex and 1.5" of 4 lb memory foam or latex/polyfoam hybrids that use 3" of more costly types of latex or memory foam) … the raw material cost of a mattress isn’t the most important part of the “value” of a mattress purchase so only you can decide which one is the best value for you. The most important part of “value” would be PPP followed by the durability of the materials followed by the other criteria that are most important to you. I would also consider whether you are comfortable with a “one size fits all” mattress where it either works or it doesn’t and where logic says that the percentage of people where a mattress is “ideal” will be much lower than marketing information may suggest. Part of this would depend on how sensitive you are to different types of materials or designs and where you are in the range between “I can sleep on anything” and “princess and the pea”.
At the very least I would have one or two other finalists (even if all of them are online) where each of them would make a good choice based on your “best judgement” and then make a final choice between them. For me … a big part of the “value” of a mattress purchase is relative to what you are comparing it to and your frame of reference.
Phoenix