"How much are these apples?"

Translation: 这些苹果多少钱？

[LaBiciEsMia]

Does adding 是 make it gramatically incorrect, i.e.: "这些苹果是多少钱“ ？

[DheerajBhaskar]

I'd left the same comment in a similar question. Hopefully someone answers

[Gustopher94]

Because 'these' denotes the existence of more than one apple, where as 一个 denotes one apple only.