The spell Commune specifys
(incense and a vial of holy or unholy water)
obviously, holy water and incense have a definition but I couldn't find a definition or cost for "unholy water". Since it is assumed that a component pouch/focus ignores material components without a GP cost, would you have to pay for the incense and holy water?
What is "unholy water"? related to the definition of unholy water however no RAW answer
As written, a component pouch or a focus replace all of these components at no cost to the caster:
Casting some spells requires particular objects, specified in parentheses in the component entry. A character can use a component pouch or a spellcasting focus (found in “Equipment”) in place of the components specified for a spell. But if a cost is indicated for a component, a character must have that specific component before he or she can cast the spell.
Since no cost is specified for the components of commune, either a focus or component pouch can replace these components without concern for if you have gone through roleplaying of finding these things. The idea here is that these things are standard fare for clerics, and any cleric would keep these things in their component pouch anyway.
That said, material components without cost provide an optional roleplaying experience for the caster. If you want (or if your DM requires it), it can be fun to keep track of these things, or to roleplay the interactions necessary to obtain the incense and (un-)holy water. But to be clear, these interactions are not required by the rules, but may be required by your DM.