Don't receive finished goods, receive components.  Or use standard costing.

receive components is not realistic. Client receives thousands of computers for each shipment.

You can disassemble BOM's and then assemble new BOMs.

Or invoice the server as is, then credit the removed component on a line and invoice the added component on a line.

So your invoice details will look something like:

1 x  Server                           $ 2000.000

-1 x 1GB hard drive             $ -100.00

1 x 2GB hard drive             $   200.00

You could also invoice the server at the final price of $2100 and the component can be a zero value charge, whatever works for the client.

There is no magic bullet here... the client is going to have to do some processing to reflect the change in components.

I had a client that sold computers so I've been through the process.

thanks guys for helping.

more specifically, how does system "know" the cost of removed 1GB hard drive, since it has never been separately received to begin with?

They purchase Server as a whole, say for $900. It has two 1GB Hard drives in it. A customer wants only 1 hard drive instead, so they would take remove 1 of them, and "assign" $100 cost to it. In the end, they would like to see: the true cost of server is $800, and 1 hard drive available at the cost of $100.

Client is currently using Sage Pro, and they said this wasn't a problem in Sage Pro at all. They can simply remove "any" components and assign the costs to the components, and everything gets updated properly. We haven't seen it in action yet.