I believe you are handwaving the problem away here.
Have you ever tried to go to a mattress shop and ask them about spring density, the gauge of steel used, and the spring layout on a mattress? These information is totally proprietary and the average salesman wouldn't know either.
This information could be obtained by users/consumer review companies by reverse engineering (or purely testing) products to make numerical comparisons of various properties.
In the case of mattresses, the size of springs isn't as relevant as the amount of sag in the bed when a 70kg person is lying on it. A more advanced measure could be the evenness of weight distribution across the mattress. These measurements are unlikely to be performed by consumers because of the time and effort required. However product review companies could generate revenue from selling consumers detailed comparisons/analysis of products.
Have you ever tried to go to a mattress shop and ask them about spring density, the gauge of steel used, and the spring layout on a mattress? These information is totally proprietary and the average salesman wouldn't know either.