Hi kenzo,
OK … that clarifies a few things.
There are two Spinal Care Bedding companies. One is a small independent manufacturer based in Gardena, CA (and is also called Good Mattress Company). Their website is here. They are NOT owned by Serta and are completely independent. They make some good quality and value mattresses including the one you are looking at. These are the ones that are carried by Dreamland.
The other is the one that is owned by Serta. Their website is here (dot com instead of dot net). Like their parent company … they are not in the same quality/value range as the one in Gardena.
When you were mentioning a “really cheap” mattress I was assuming that you were talking about a sub $500 mattress and the specs you listed didn’t seem to fit this budget range. I wanted to make sure you weren’t buying a liquidation or used mattress. The prices you are listing are more in line with what I would expect and I would consider it to be a good quality and value choice with no weak links in the mattress.
This is also a very uncommon pocket spring with a very high coil count that you don’t see much in the industry.
I have also talked with Bruce at Dreamland Mattress Discount and think highly of his knowledge and experience and they are also a forum member (see this thread).
It’s good to hear you are considering the “good” Spinal Care instead of the “other” Spinal Care 
I’ve also added them to the Los Angeles list here because for some reason I neglected to do so when I first talked with Bruce so thanks for bringing them up.
Phoenix