Hi Nv03M3,
From a material value point of view all the mattresses made by the same manufacturer would generally have similar “value” although the mattresses in higher budget ranges will often have a slightly higher margin. Having said that … a mattress is much more than just a commodity that can be assessed by the cost per inch of foam or the cost per pound of fabric (see post #13 here).
Post #2 here has more about the differences between a latex/polyfoam hybrid and an all latex mattress that may be helpful in your choice and post #2 here and the posts it links to is a reply to the same question and would also be worth reading.
Phoenix