Basically because we were 1st-time authors. We hired a professional editor and paid him to edit our first draft. Then, we shared that draft with readers and it just wasn't good enough. So, we had to go back, re-edit the entire thing, and then pay for the editor to go over it all again.

Pretty frustrating, and the reason why editing was likely 2-3x more than it should have been. However, it also resulted in a much better book.