The suggested pricing rules for creating magic items suggests that items that are continuous or use-activated should cost 2,000 gold * the level of the spell they duplicate * the Caster level of that spell.
The text also says level zero spells should be treated as half level spells. By that formula a use activated launch item weapon should cost 1,000 gold and usable five times a day. However, many items do not follow these guidelines as the effects they give are either much stronger or much weaker than this price tag would suggest.
Assuming the purpose of this item is to create an alternative to a crossbow that can fire anything eligible for the launch item cantrip and that still requires both an attack and an attack roll to use, would 6,000 gold be a balanced price for it to work 30 times each day?
If so, would it also be balanced to allow this property to be added to an existing crossbow? Or for a separate item with this property to be enhanced like a ranged weapon?
For context, a Gnome Artificer (the 3.0 class from Magic of Faerûn) is able to make a non-magical, 50-use version of this item for 1000 gold. Their version also takes up either the belt or cloak slot unless they double the price. So for 6000 gold they could create a version that is usable 150 times before wearing out and needing to be repaired (which costs half as much as building a new one)