Bests & Worsts Reviews from Amazon

I bought my first one of these over a year ago, and it was about 18" from the floor to the start of the top of the mattress, and was about $150. About 6 months later, I bought another one, and a third one a couple weeks ago. I use them all for my grands with a "topper". They work well and are comfy. For each mattress, it has cost less than the previous one, and also each mattress is 1" shorter from the floor to the start of the mattress top than the previous one I bought (18", 17", 16"). The first one I bought is the most comfortable, and works well for adults. I put a "topper" on each one. I did have a small hole develop in one seam, and worked with a glue to close it, and its has not reopened. I am a bit confused as to why the gradual decrease in size, cost and comfort of this mattress over the past year. I can see no discernible difference in the label, product number, name, color, look or anything, other than the number of inches from the floor. I would have preferred to pay more and have them all be identical to the first mattress I bought. The 16" is not comfortable for adults. The 18" would be, however, this bed was advertised as being 18"