In Dungeon Crawl Classics, the core rules are clear that the cost of arrows is 5g for 20 and the cost for sling stones is 1g for 30 (p72). However, as far as I see the Umerica variant has no cost for ammunition for the sling or any of the bows. Am I missing something?
I have noted Umerica p118 Slingshot says "Like the slings of old, any small, weighty, and balanced object can be used as ammunition for the slingshot." Without knowing the history of the weapon it is a logical leap this could apply to the sling however still leaves arrows silent.
My GM has said we can use the cost in the core rules, however, this answer is not sitting well with me because in Umerica the cost of all the basic weapon tables (p116) and even firearms (p122) is in silver (vs the DCC core rules, they are all in gold). An argument could be made that slings/bows are easy to find but ammunition isn't, however further, the firearms section says "Ammunition Standard firearms ammunition generally costs 1sp per round." which further suspends my disbelief - would a bullet be the same cost as a sling stone and be cheaper than an arrow?
So I appeal to you, internet, is there any further guidance (preferably from a DCC source) that may I may show my GM? ("my group does..." answers are fine however since my GM already made a ruling, I'm not sure it'll help me; that is, I am looking for a source rather than an opinion to start a debate, which I already have)