Usually, colonialism hasn't been about "customers."
I don't think Europeans came to the Americas and Africa thinking, "Boy, I can't wait to sell these guys some fine silverware and clothing."
They mostly took stuff off somewhere else to sell it to other Europeans. You know--people who had money. Unfortunately, this stuff sometimes included Africans.
Again, we should be so fortunate that a space-faring civilization takes any benevolent interest in us at all. Aside from tourism potential, they really wouldn't have to.
Now that I think about it, tourism, including crafts and things, would be the one thing we'd have to sell. Certainly a lot of "primitive" people have figured out that this is a fairly easy way to separate the "advanced" people from their cash.