It is going to depend greatly on who is brokering the name.
I know some who charge (and get) 30-35%. These are typically attorneys who do all the legal paperwork, contracts, etc.
For private brokers, 15%-20% is not unheard of or unreasonable.
If you start getting higher profile brokers (bloggers with large followings) expect top ranges of brokerage fees that you are seeing here.