An upvoted question or answer earns +10. But if the author has decided to make it a wiki for betterment of the post or has been made wiki by the community moderators, then reputation per upvote is straight 0! This is a drastic difference.
There are several wiki posts where the original author has edited more revisions.
Proposal: The original author should be awarded +1 or +2 or whatever is deemed appropriate for every upvote on wiki answer.
As a good side effect, this will also help the author to know any voting activity on that post.
Don't have any specific suggestion for downvotes.