Hi Gynna,
Unfortunately there isn’t a “formula” that can be used to assess or “calculate” value because there are so many variables and criteria involved that are more or less important to different people that may be very different from someone else and because the “value” of a mattress purchase is always relative to the other finalists you are considering or to the other mattresses that are available to you in the area or online.
There is more about the 3 most important parts of the “value” of a mattress purchase in post #13 here which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on suitability, durability, and all the other parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase to fine tune the mattress or the exchange return options that are available to you).
While I can’t speak to how any mattress will “feel” or whether it will be a good “match” in terms of PPP for someone else (and this is the most important part of the “value” of a mattress purchase) … as you mentioned the Conforma doesn’t have any obvious weak links in its design relative to more average weight ranges but for those that are in a higher weight range (more than the lower 200’s or so) I would look to reduce the thickness of any memory foam that is less than 5 lb density and for a higher density base foam as well. While a 1.5 lb base foam will “probably” be ok … In this budget range a higher density base foam would also be a more reasonable “expectation” and would also be a less risky choice in terms of durability.
Phoenix