I was looking for a twin mattress and found this,
LINENSPA 6" Innerspring Twin Mattress [amazon.com]
for $59, has decent reviews and priced the lowest ever(ref: camelcamelcamel).
It was made interesting for me, I also had the promotional discount (YMMV) - AXPFURNITURE
good for Furniture - 30% off (upto $15) in select categories when you use Amex Membership Rewards points.
So my total was $59 - 15 = $44.
Even without the promotion for some, this price($59) is good with free shipping.