I would've given this a plus one in the past, but I feel like this is not really that good of an idea anymore. Find a desert, place torches, let the entire desert fall, gain ton of money. Plus flint would need a price too, which does not have a price for a reason.
I would not give gravel or a sand a value, I prefer to have some items in firm control of the player economy so that players can set prices purely based on supply and demand without having to worry about a /sell hand value at all. But that's just what I prefer.
By that logic dirt should be worthless, too. wat You're making zero sense. you don't just let the entire desert fall. In fact, that's more work than just digging it out with an eff5 shovel.
I don't mean to necro, I think this is relevant, as it might be an alternative way to make gravel worth something without placing an arbitrary /sell value: https://www.ecocitycraft.com/forum/...d-new-idiotic-namechanger-forum-medal.163890/