Hi Johnf59,
From a “value” or “materials” perspective yes, it is worth the extra money. The materials in the Organic Dream are more costly than the materials in the other two (they have 3 latex mattresses on their site).
The real question though is whether the difference in price is worth it to you and this is a matter of what I call your “value equation” which is all about what is more and less important to you. All of the mattresses that they sell would have similar “value” if value was only based on the cost of the materials they contain.
Part of this is how well each one fits your needs (Pressure relief and Posture/alignment) and preferences (you can see more about this in post #2 here). For some … more natural materials would be worth it while for other it wouldn’t.
The Evergreen uses a 5" blended latex core, 2" of natural Talalay on each side and then an inch of polyfoam on each side, and has a bamboo or Ingeo core.
The Natural Escape uses a 5" blended latex core, 2" of natural Talalay on each side and then cotton and wool in the ticking/quilting.
The Organic Dreams uses a 3" natural latex core with 3" of natural Talalay latex on each side and then cotton and wool in the ticking quilting.
The best way to choose would be to personally test them for how well they fit your needs and preferences, to decide whether the benefits of more natural materials and wool are worth it for you, and/or to talk with them about which may be the best choice for you.
No offense taken … and the question has been asked many times. It’s good to be skeptical 
There is a lot of information on the site about how and why I invite certain manufacturers or retailers to become members (not “sponsors”). In most cases I was posting about them in other venues long before this site was even developed or being considered. Among many other places (in the forum and on the site) … you can read more about why they are invited in this article, in the first article on the front page of the site, and most recently in the forum post #5 here. Basically it is a form of recognition of their quality, value, and service (which is mostly self evident for consumers who know which materials are better and worse quality and how to make meaningful comparisons between mattresses based on the information on the site) and that they are among the group which I consider to be among the “best in the country”. Their membership has nothing to do with their “value” or whether I “promote them” and as you can see from the many hundreds of posts on the forum which identify non members all around the country as good sources (or at least possible sources) of value … I identify better value choices wherever I see them … regardless of their membership.
Hope this helps
Phoenix