Hi WonkyBent,
Welcome to the Mattress Forum! … and I’m glad that the information here has been helpful for you
I would be aware that there is no such thing as “quasi-organic” or even “natural” memory foam and if you come across these types of descriptions that they are “misleading marketing” more than anything else. Memory foam is a synthetic material that is made mostly from petrochemicals although some manufacturers do use a plant oil based chemical derivative to replace a relatively small percentage of one of the two main chemicals that are used to make polyfoam or any of its derivatives such as memory foam. There is more about so called “bio based” foam materials in post #2 here.
The number of coils in an innerspring are only one of many specs that can affect how an innerspring affects the mattress and by itself it will tell you very little about the mattress. Your own personal testing or experience on a mattress is the only reliable way to know the effect of a specific innerspring in combination with all the other layers and components in a mattress. There is more about innersprings in this article and post #10 here. There is also more about some of the differences between latex support cores and innersprings in post #28 here.
There are some sources for innerspring (or pocket coils)/latex hybrids in post #2 here and some of these (such as Berkeley Ergonomics and Naturepedic) also make mattresses that use microcoils in their comfort layers as well. There may also be some local manufacturers that make mattresses that meet your criteria and if you let me know the city or zip code you live in I’d be happy to let you know about any of the better options or possibilities I’m aware of in your area as well.
That’s too broad a question to be able to answer specifically because the “value” of a mattress purchase depends on many things including the specifics of the mattress and the specific materials and components inside it not just on the general “category” of materials. It would also be relative to each person’s criteria and the parts of their personal value equation that are most important to them along with how a mattress compares to the other “finalists” that they are considering or that are available to them. I would consider all of the mattresses in the previous link to be in a reasonable value range but as you can see there is a big difference in their prices. There is also more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful “value” comparisons based on the criteria that are most important to you.
Phoenix