I have wrote about this a few days ago
http://community.vsl.co.at/forums/p/27315/178658.aspx#178658
You have to review the discout you get when you own already articulations for an Instrument
In most the case the articulation you already own are in the DVD standard, so you pay the twice the articulation ;o(
It will much more attractive for your clients, and much more faithful, to put de reduction on the DVD of the instrument
If the instrument is in the standard you get deduction in the standard DVD, if it is in the extended you put the deduction on the extended DVD