This wont work, as skyblock uses the grass currency, there really is no fixed price for selling items. Most to all prices are made by the playerbase and a sell system like this just wouldnt work. (May on eco)
I like that the fact that the economy on skyblock is determined by player base purchasing and selling. Introducing this sell chest would kind of remove the aspect of game play that is earning grass through selling items to other players. I will be no supporting this idea, but thank you for contributing to the evolution of this server.
Seems like a cool idea, but there arnt really any actual prices, most prices are player made, this would be a great addition on eco tho!