This is the most common method. And it can work. It doesn’t work all that well, however. So we’re going to make short shrift of it.
If an acquisitions editor is doing this, you should usually divide the estimate in half. All AEs fall in love with their babies, and so they should. But it doesn’t make them the most objective judges.
If it’s done by a marketing team, look at the person’s track record. Most will estimate high, but some are consistently pessimistic.
When you do this, somewhere deep down inside you, there’s a little calculator doing something a little like the method in Part III. Essentially, you’re looking at comparables, estimating their sales, and then adding or subtracting to allow for factors like the economy, pricing, relative quality of the cover, the reviews, and the content, and the amount of marketing that the author and your marketing department are likely to manage.
What factors do you toss into the mix?