Dear N:

You wrote:

1-How much will it cost to go to each of these museums?

Can’t this sentence mean two things:

a-How much will it cost to go to ALL of these museums?

No. It could be asking for an itemized list, but the question is about EACH museum. This question is asking for a TOTAL only.

b-How much will each of them cost? (In this case we would be asking for a list of prices.)

Yes, this is what it is asking.

If the sentence cannot mean ‘b’, how can one formulate ‘b’?

2-How much will each of these museums cost to go to?

This is asking the same thing. #1 is a bit more direct and clear.