Hi Jc9595,
This would really depend on the person and your own risk tolerance because different people would have very different criteria and very different opinions.
I would make sure that you have tested the mattress very carefully (hopefully using the testing guidelines in the tutorial) to make sure that you are confident that it’s a good match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). Other than that … the mattress you are considering is most likely a comfort return or worse yet a warranty return or it could have other “hidden” issues so it would depend on how you feel about sleeping on a used mattress or how you feel about the risks involved in buying a mattress where you would have no recourse if there were any defects in the mattress and/or you needed to replace it or if your sleeping experience indicated that the mattress wasn’t a good match for you in terms of PPP. There would be very little value in buying a mattress if it’s not a good match for you in terms of PPP and you don’t sleep well on it no matter what the price or the quality and durability of the materials inside it or the mattress as a whole.
It would also depend on whether you tend to prefer sleeping on memory foam or latex (which is strictly a preference choice) because all of the mattresses you are considering use high quality materials and there are no lower quality materials or weak links in any of them so there would be no advantage in terms of durability if you purchased the Tempurpedic and the cost would still be higher than the other options you are considering. There is more about the pros and cons of latex vs memory foam in post #2 here but the best way to know which type of material or mattress you tend to prefer is based on your own local testing or your own personal experience.
There is more about the 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 all the parts of your personal value equation that are most important to you).
There is also more about some of the things you can check for if you are considering buying a used mattress in post #2 here and if you are considering buying a mattress from a liquidator or clearance store that sells used or returned mattresses then there is more here and here and here that I would read and that may be helpful as well.
Buying a mattress that someone else has probably returned for “unknown” reasons would certainly be a very risky choice when you have absolutely no recourse after the purchase so it would really depend on your risk tolerance and whether the risks and/or the higher cost compared to the other options you are considering would be worth it to you.
Phoenix