I personally am a fan of @gailcalled 5 cinder blocks and plywood idea. Though really those metal frames that you get I have never paid for them, see family friends and recycling transit sites. Plywood is more expensive then it should be but fairly adequate for box spring spring alternative. But to refer back to metal frame: also imagine you can get cheap through yard sales and craigslist.
The bed in a box idea that you posted reminded me of one I bought for a cabin 6 or 7 yrs ago. It was comfortable but very heavy. Also it couldn’t be supported by metal frame w/o box springs. It was fine at first but I got tired of having my bed on the floor. Felt like a kid, difficult for bed making and romantic pleasure. And a pain in the butt to move once out of the box, no handles and floppy plus heavy….
Better yet is camping alternatives. They are getting more comfortable these days. Double usage will get a good resale, or can be brought with. As they are made to be compact. Also air mattresses again they are improving. Fairly cheap and are always good for visitors even after you have a real bed. (As long as you don’t have an animal with sharp and pointies.)
Night stand try milk crates if you really want to save. You can use a piece of cardboard on top to create a flat surface and cover with fabric stackable to the desired height and width, also works for dresser in a pinch, but those rubbermaid drawers are a step up and serve for good storage for a more permanent domacile. But I generally was always a hanger over a folder on any day. Craigslist is a nice alternative as well and no worries about the yuck germ factor.