Hi there,
I believe that I have a solution for you.
1) Create the relevant item with the following configuration:
-Costing method : Average; this is to account for the fluctuation in cost,
-Unit cost = 0.00
-Unit price = 0.00
-Select the Gen. Prod and VAT. Prod posting groups that apply to your situation,
-Create a dummy vendor and apply to the item,
-Ensure the remaining, important information is completed.
-If you are multiple variants of the items, such as different sizes, you will need you use the variants and stock keeping units functionality.
2) Create a purchase order against the dummy vendor.
-Enter the vendor's correct details into the purchase order (General, Invoicing tabs),
-Add a purchase line for the item in question and define the "direct unit cost" (If 0.00 then leave blank) and a quantity.
-Define a "Qty.To Receive".
-Click functions > Release,
-Click Posting > Print and post > Receive and invoice.
At this stage you will have a zero cost inventory for the item. Now all that is left to do is to create and post a sales order.
3) Create a sales order,
-Define the customer: you may need to create the relevant customer(s), however there are two options:
1.Create a new customer record each time you sell the product to a different person.
2. Create a generic customer which can be used to post all sales against.
-The application method (Invoicing tab) for the customer should be set to "Apply to oldest". This will ensure that you do not have to complete application postings between the customer ledger entries and the posted sales invoices.
-Create sales lines within the sales order for the items you are selling; define the relevant item variant where applicable.
-Define the "unit price" and quantity,
-Click functions > Release,
-Click Posting > Print and post > Shipment and invoice.
Once you have posted the sales shipment and invoice; the item's inventory will reduce and the relevant value postings will be applied to the G/L accounts which are linked to the item's posting groups.
Hope this helps!