We have Murphy beds in both of our spare bedrooms. Both are made of real wood, not composite, and can support any queen sized mattress. We have high end mattresses in both, and they are very comfortable. The problem is that anything you buy around here will be in the $2,000-$3,000 range for cheap composite, and upwards of $4,000-$5,000 for real wood.
I bought kits from
WWBeds Custom Furniture | Arkansas | Murphy Beds. They are made of real wood, and you can get them as low as $1,500-$2,000. Below is a pic of one of mine:
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