Only have you ever seen a publisher's boilerplate contract - the one they give you if no one has gone through it and changed it to make it more even? It gives every possible right to the publisher, including the right to make action figures based on your characters, or theme park rides based on your plot.
So this person sold worldwide hardcover and paperback rights, film rights, audio rights, action figure rights, theme park rights, etc. etc. - for $6.500.
If for some reason you ever have an offer but no agent, do yourself a favor. Get one. They will at least negotiate it up enough to cover their 15%. Otherwise, it will be you vs. the publisher, and the publisher is a lot bigger and more experienced than you are.