Product Average Price From Invoices

This module computes, from posted invoices, two average prices and stores them on product templates and product variants:

• Average Purchase Price (APP), from vendor bills.
• Average Sale Price (ASP), from customer invoices.

Each one is a weighted average: the untaxed subtotal of the invoice lines divided by the invoiced quantity. Taxes and added costs (landed costs, for instance) are excluded, and so are refunds, as a returned quantity is not a price the product was traded at.

Both prices are company dependent: every company gets its own figures, computed from its own invoices and with its own window settings, so each one sees the prices it traded at.

Instead of a fixed period, an expanding window is used: the last 30 days are checked first and, while no invoiced quantity is found, the window is widened 30 days at a time up to 360 days. The first window with data wins, and the range it covers is stored next to the price, so the figure is always readable in context. Both the step size and the maximum number of steps are configurable.

Templates and variants are computed independently: a template averages the invoices of all its variants over a single window, a variant averages only its own. Because of that, they may end up using different periods.

Values are stored, not computed on the fly. They are refreshed by a daily scheduled action, and on demand from the product form, where the journal items behind each price can also be opened.