alt Hacker NewsSome sci fi author (I forget who) pointed out that in a space faring society, the most valuable materials are biological materials. Once you have access to comets and planets, you'll have, for all intents and purposes, an infinite supply of gold, diamond, ruby, etc.
Wood however... You're not gonna find a lot of wood in space.
There is absolutely no reason for alien life to have evolved the same biological materials that we have. But also, a space faring species that can build an AI probe capable of remaining functioning for the many years an interstellar journey takes, is also likely to be capable of building habitats that can grow their biological materials. It'd be much easier than shipping those materials over from another star.