Hi MrM1,
This certainly isn’t correct at all!
There are many “versions” of latex and there is more about the different types and blends of latex in post #6 here.
Talalay latex comes from either Radium or Latex international and is available in either a blended version or a 100% natural version (which is more costly) and a few others as well such as gel infused Talalay, graphite infused Talalay, and even slow response talalay.
Dunlop latex is either made in a mold or with a continuous pour process and there are many different blends of Dunlop latex as well. Dunlop is made by many manufacturers around the world and there are many suppliers of good quality Dunlop latex.
All of these come in a wide range of firmness levels and mattresses that use them come in a wide range of designs and with other components (such as the cover) that can also play a significant part of the cost and the feel and performance of a mattress.
There is also more about the general differences between Talalay and Dunlop in post #7 here.
Phoenix