Hi ekrolik,
There is more about the many variables that can affect how a manufacturer prices their mattresses in post #14 here but in most cases the information you would need to answer these types of questions in any specific way won’t be available to you. The My Green Mattress Organic Dreams uses 100% natural Talalay in all the layers which is a more costly material than 100% natural Dunlop used in the Brooklyn Bedding Essence and it is also finished on both sides so the materials in the cover and quilting would be more costly. It also takes more time to manufacture a two sided “finished” mattress that is tape edged on both sides. There is more about the pros and cons of a two sided mattress in posts #2 and #3 here.
In more practical terms though … there is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful quality/value comparisons between mattresses based on all the parts of your personal value equation that are most important and have “value” to you.
Phoenix