Hi DaveC,
Foam Source has a range of all latex mattresses that are all significantly less than $3000 (and some are also less than the mattresses you are already considering) so they would certainly be worth a visit IMO if you are interested in testing a wide range of latex mattresses to see how they compare to the mattresses you are already looking at.
While other people’s comments about the knowledge and service of a particular business can certainly be very helpful … I would also be very cautious about about using other people’s experiences or reviews on a mattress (either positive or negative) or review sites in general as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you and in many if not most cases they can be more misleading than helpful because any mattress that would be a perfect choice for one person or even a larger group of people may be completely unsuitable for someone else to sleep on (even if they are in a similar weight range) and reviews in general certainly won’t tell you much if anything about the suitability, quality, durability, or “value” of a mattress for any particular person (see post #13 here).
Two sided mattresses can certainly be more durable than a similar one sided mattress but there are also advantages to some one sided designs as well and they can also be a very durable choice if they use very high quality and durable materials such as latex. There is more about the pros and cons of one sided and two sided mattresses in post #3 here.
Phoenix