If I buy a beer for $3 on a train, is the primary purpose of that $3 "transport", because practically nobody gets on a train just to drink beer? What if that $3

If I buy a beer for $3 on a train, is the primary purpose of that $3 "transport", because practically nobody gets on a train just to drink beer? What if that $3 is merged into the total cost of your ticket and you get the beer included? The fact that it seems airlines do underchage for cheap seats and overcharge for expensive ones is irrelevant - I already pointed out that ticket sellers can go in either direction on this. The point I am making is that you are getting a tangible thing that is more expensive (e.g. a nicer seat) - whether you are being ripped off or not is another matter.