Questions & Answers about Мы уже купили по одному билету на концерт.
It means one ticket each or one ticket apiece.
So Мы уже купили по одному билету на концерт means that every person in мы bought one ticket. It does not mean that the group bought only one single ticket total.
Because по одному is a very common Russian way to express distribution: one each.
Compare:
- Мы купили один билет = We bought one ticket (just one total)
- Мы купили по одному билету = We bought one ticket each
The preposition по often gives this distributive meaning.
Because after по in this distributive meaning, Russian commonly uses the dative case.
So:
- билет = nominative
- билету = dative singular
That is why you get:
- по одному билету
Both одному and билету are in the dative singular.