If you download this from a browser, put it into your world's datapack folder. If you install this from curseforge, install the mod "Global Packs" to have the datapack working. If the mod "Global Packs" isn't available for a specific version, move this datapack from your resourcepacks folder into your world's datapack folder.
What this datapack does is setting everyone's statistic "crafted vault crystals" to 1 every 10 seconds, this is because the amount of items required by the vault altar depends on the number of vault crystals crafted, so setting it to 1 repeatedly will lower the item demand as soon as it rises.
If you already started a world and you put this datapack into it, the item demand decrease will apply after completing your current vault crystal recipe.
Works for VH 13, 14, 15.