I don't understand why some company doesn't just put 3" of good foam and a decent cover and sell it that way? 3" of latex from Rockymountain costs $320 (queen). That is retail including shipping. Yes, that is one 3" piece but I don't think their costs would be any different for 2 1.5" pieces of different firmness since they buy in quantity.
Put on a nice cotton / wool top for $200 - retail. They will save something on the junk they don't include, so the total cost would be less than $500 more. So, this $800 mattress set could be sold for $1300 with much better quality on top. Yeah, the box springs, etc. aren't the greatest, but still it would be a decent quality mattress.