A2X has taken an average/blended cost model for our cogs function. Cost prices can be updated as often as you need and those average costs will be applied from that moment forward. Users generally update their average costs on a per settlement or monthly basis.
Currently, A2X is primarily focused on the financial transactions, sales, fees, charge-backs, reimbursements etc. COGS is a function of sales - it is the cost price of the sales you made.
However, as you would know using a dynamic cost model, a number of inventory transactions can happen at different times and involve FIFO/LIFO situations etc.
These can all have an impact on your accounting, too. For example, when a return comes back into stock sell-able, or when Amazon damages a unit.
Today, those inventory transactions are typically captured by accountants in the standard inventory accounting approach:
Opening stock + purchases - COGS - adjustment = closing stock.
Our feedback from users was that when users out-grow simple costing, they typically move to one sort of advanced inventory tool to manage vendors, purchase orders and costing schemes (LIFO, FIFO etc) separately from their accounting system.