The amount you pay a professional editor depends on the length and complexity of your manuscript, as well as the editor's experience and qualifications. As a general rule of thumb, you can expect to pay about 1 to 2 cents per word for a basic copy edit, and 2 to 3 cents per word for a more comprehensive edit. So, for a 80,000-word novel, you would be looking at paying anywhere from $800 to $2,400.
Of course, there are a lot of variables that can affect the cost of editing, including the type of edit you need, the turnaround time you need, and the editor's experience and qualifications. If you're not sure what kind of edit you need, or how much it should cost, it's always best to ask around for recommendations or get a few bids from different editors before making a decision.