Puzzle ZQFL 

Workings

Hint
Start by looking at the consonants and vowels (AEIOU).

Answer
65 tonnes.

Reasoning
Vowels (AEIOU) are worth 3 and consonants are worth 5, added together and then multiplied by the number of ingots.

IRON = V + C + V + C = 3 + 5 + 3 + 5 = 16, and 7 of these = 7 x 16 = 112 tonnes.

COBALT = C + V + C + V + C + C = 5 + 3 + 5 + 3 + 5 + 5 = 26, and 4 of these = 4 x 16 = 104 tonnes.

GOLD = C + V + C + C = 5 + 3 + 5 + 5 = 18, and 3 of these = 3 x 54 tonnes.

TIN = C + V + C = 5 + 3 + 5 = 13, and 5 of these = 5 x 13 = 65 tonnes.