(2) And another question: What is the strech goal "metal credits #2" about?! What and how many coins are included?
Metal credits #1: costs $15 and gives you 32 One Credit coins and 16 Five Credit coins. You are paying around 31 cents per coin.
Metal credits #2: costs $5 and gives you EITHER 10 One Credit coins OR 10 Two Credit coins OR 10 Three Credit coins OR 10 Five Credit coins OR 10 Ten Credit coins. You are paying 50 cents per coin.
So to get coins in every denomination you would need to spend at least $30: $15 (One and Five) + $5 (Two) + $5 (Three) + $5 (Ten). You are paying around 38 cents per coin.