Well, after reading your post and other member's reply, i can tell your model lacks only one or two things. Which are liquidation problem like why the amount will be provided by everyone and the data shown to us will not be live. Second is the scammers. So, how one can solve such limitations.

i think ZK-proof mechanism might be used to identify that the seller of any goods or thing has the legitimate thing and on the other side the person has the right and legit amount. This, will decrease the fear of getting scam. As, this Zero knowledge proof mechanism will also secure your personal identity too.

And to get the live reserves information instead of just getting a screenshot information you could use chainlink or Harmony platforms. But i have no experience of any of them. So before selecting one you must ask here.