No, I agree that there can be reputational cost. But how much it costs your reputation is even more subjective, as it depends on what the content is that you are reposting, and whether it is in alignment with the reputation you have built up, therefore reinforcing it, or at odds with and therefore hurting it, or somewhere in-between. None of which can be easily quantified.

Someone of character may not be willing to repost content that could damage their reputation, regardless of how much they are offered to do so, while they will gladly repost content that reinforces their reputation for free.