>>these additional costs cannot be predefined to exact amount.

Having read that, If your landed cost are somewhat predictable you may want to use the estimated method instead of the actual method.   Then you charge the actual cost against the estimated accruals.   At the end of the year, or periodically,  you adjust your estimates to match them  as close to the actual as possible.

This is a lot less work.  

Some might argue is it less accurate but others might argue that because you are passing through the estimated cost to the work order as you said "As we already issued those materials into production, there is a variance (under/over value)" the actual cost of that work order is more accurate with SOMETHING absorbed than nothing absorbed and the amount ending in a variance account or just pushed into cost of production.

It looks like you just under costed you work order by $ 6,000 above.

This method was further enhanced in version 9.0

Advanced Purchasing Costs Management

A new feature on the management of APC (Advanced Purchasing Costs) enables users to foresee the purchase costs for international imports using international standards (incoterm) or inland purchases.
This feature allows two methods to manage calculation of purchase costs:
• Landed cost coefficient (coefficient + cost per unit)
• Cost structure
The objective is to estimate the purchase cost of goods, along with the logistic operations included in the supply chain. 
The logistic operations can span a range of different steps: from packing, loading operation, export customs, to post routing.
The landed cost coefficient has been added to unitary and fixed costs to calculate the product purchase cost. The product purchase cost is composed of a cost structure including different added costs. The purchase cost can be defined per site. The costs can
be updated by purchase invoices.
Benefit: Ease the tracking of purchase costs to ensure profitability with more flexibility of
costs setup

>>these additional costs cannot be predefined to exact amount.

Having read that, If your landed cost are somewhat predictable you may want to use the estimated method instead of the actual method.   Then you charge the actual cost against the estimated accruals.   At the end of the year, or periodically,  you adjust your estimates to match them  as close to the actual as possible.

This is a lot less work.  

Some might argue is it less accurate but others might argue that because you are passing through the estimated cost to the work order as you said "As we already issued those materials into production, there is a variance (under/over value)" the actual cost of that work order is more accurate with SOMETHING absorbed than nothing absorbed and the amount ending in a variance account or just pushed into cost of production.

It looks like you just under costed you work order by $ 6,000 above.

This method was further enhanced in version 9.0

Advanced Purchasing Costs Management

A new feature on the management of APC (Advanced Purchasing Costs) enables users to foresee the purchase costs for international imports using international standards (incoterm) or inland purchases.
This feature allows two methods to manage calculation of purchase costs:
• Landed cost coefficient (coefficient + cost per unit)
• Cost structure
The objective is to estimate the purchase cost of goods, along with the logistic operations included in the supply chain. 
The logistic operations can span a range of different steps: from packing, loading operation, export customs, to post routing.
The landed cost coefficient has been added to unitary and fixed costs to calculate the product purchase cost. The product purchase cost is composed of a cost structure including different added costs. The purchase cost can be defined per site. The costs can
be updated by purchase invoices.
Benefit: Ease the tracking of purchase costs to ensure profitability with more flexibility of
costs setup

Thank you very much Stephen for your elaboration on calculating of the landed cost. This is very helpful for us to get an idea on estimating the unit cost.

Great.   And thank you for letting Sage City know that it helped.