Hi tsbuhr,
There is more about the different ways that one mattress can “match” another one in post #9 here that may be helpful. I would keep in mind that a mattress can be a good approximation for another one in terms of comfort/pressure relief or alignment/support but can have a different “feel” or design. It may still be a good idea to test the current Tempurpedic models in person so you have a better sense of how closely they match the mattress you are sleeping on before you decide on which mattress to purchase that may itself have some differences in how closely it matches one of their current models.
There is also more about the most important parts of the “value” of a mattress purchase in post #13 here.
There is more about this in post #14 here. In very general terms higher quality/density foams are more costly than lower quality/density foams of the same type although there are other factors involved in the raw material cost of foams such as certain performance benefits that are part of the foam formulation besides density as well.
I would also keep in mind that the return or exchange policy is part of the built in to the cost of a mattress will have an effect on the price because the majority of customers who don’t return a mattress would be paying for the minority who do. There are differences between the return and exchange policies for each manufacturer in terms of the length of the trial period, the minimum usage time before a mattress can be returned or exchanged, and the costs involved in returning a mattress that may be important to you in the minority of cases where this becomes necessary. The Restava return/exchange policy is here, the Select Foam return/exchange policy is here, and the Christeli return/exchange policy is here.
Phoenix