Hi HudaThunkit,
You may be looking at their synthetic Dunlop latex that uses a continuous pour process and is made by Mountaintop Foam which is a less costly version of latex compared to Talalay or 100% natural Dunlop. You can read more about the different types of latex in post #6 here.
If you go to the Spindle site and click on either the Blue Shoal (which has 6" of latex) or the Abscond (which has 9" of latex) and choose the size you are looking at from the menu then you can choose either synthetic or 100% natural and you will see the price change to get a better sense of the relative difference in cost between their synthetic and 100% natural Dunlop . They also use polyfoam in their quilting which is a lower cost material than the wool that some other manufacturers use. (Note: Spindle is now only using 100% natural continuous pour Dunlop in their mattresses and have changed to a wool quilting as well)
Regardless of this … like the other members of this site … they offer some very good quality/value in any of the options they have available.
Phoenix