A total of 1 review of this product on Reddit.
I don’t know exactly what you are looking for in terms of a bed. but they actually sell some inexpensive frames on amazon, that are honestly pretty nice to look at. Mattresses can be pretty affordable as well if you check out walmart, or costco, even Amazon has a few that might be in budget.
Kids don’t really need a box spring or fancy mattress because they weigh basically nothing and, are just kind of made of rubber, as your child’s willingness to sleep on the floor indicates. You can go bare bones and then dress it up with a cute comforter or quilt.
Otherwise, I suggest, during the summer, driving through some of the mid/upper class towns near you on big garage sale weekends or bulk pick up days. College age children move up and move out and they tend not to want twin beds when they do. I happen to know of at least 2-3 bed frames laying around in my friend’s parents basements going unused and abandoned.
A basic bed frame plus some bed slats you can cut yourself from the hardware store make a decent low bed for a toddler.
Edit: I’m kind of in love with this one, though I recognize that my idea of budget might be different from yours https://www.amazon.com/Headboard-Footboard-Platform-Mattress-Iron-Art/dp/B081J5SMBD/ref=sr_1_29?dchild=1&keywords=twin+bed+frame&qid=1614279886&s=home-garden&sr=1-29