If you are in the Mid-west there is a Mattress manufacturer called Verlo. They make
For a Scamp Big Bed 54" x 75" - 8 inch thick, (3 types of foam, 4 inch base, 2 inch memory, 2 inch gel infused) with a quilted cover the cost is $350.
10 inch thick slightly more.
I have no association with this company but a great price.