Which are correct:
1-How much will a trip to these countries cost?
2-How much will a tripsto these countries cost?
3-How much will a trip to each of these countries cost?
4-How much will trips to each of these countries cost?
Which ask about
and which ask about
b-a trip to all the countries?
I had asked a very similar question yesterday. This is a variation on the same theme. Here we have a single noun phrase: "a trip to each of these countries'.
I feel '2' and '4' are incorrect.
I think '1' is definitely and unambiguously asking about a single trip to all the countries and '3' is ambiguous... But I think this one
5-How much will a trip to each country cost?
is unambiguous and asks about individual trips.
2 is wrong because of a trips. 4 could be right- if you want to do a tour of these countries more than once or take a group of people. Admittedly, things are getting strained here. 3 is ambiguous- it could be ten separate trips or one tour.