Calculate your planning floor first
Start with your cost of doing business and realistic annual bookings. Include time spent selling, preparing, traveling, editing, delivering, and administering the business. Set a pretax owner-compensation target and an explicit additional-profit assumption. This establishes what the business needs; it does not establish what a particular buyer will pay.
If the required average sale is $800, a $400 core service needs a credible mix of additional revenue or a different cost-and-capacity model. Optional upgrades that almost nobody buys should not be treated as dependable revenue. Use actual purchase behavior when estimating the average.