PO price changes

Hi Experts,

My final Product "A" price is 300$ and has BOM components "A1" price 200$, "A2" price 100$. I had created Sub Contracting PO for final product A..it's price 300$ is automatically came from Purchase Info Record.

Later my customer wants to add one more component in BOM , Let say "A3" and its price 50$. So i changed the existing BOM to add this "A3" component and then i entered in ME22N , there the new component "A3" is added in the BOM. But the Final product "A" price 300$ is not changed.

We added new component A3 ..so A3's price 50$ also reflecting in PO net price.But its still showing $300 only. Can you please help me out. Why New components price is not updated in PO net price? What i need to do?

Thanks

Silviya