Yes you will get a discount of the diamond, not the settings I believe. Just tell them you are a PSer and they will apply the discount, it will come off the listed price not the wire price.
I don't know for sure, but if it is anything like JA it will only be a few percent, depending on the price of the stone. Like 1-4% range - not a lot, but every dollar counts!
I believe the 5% mark but that could vary depending on the price of the stone, just remember it does come of the listed price not the wire price. But every cent does help Good luck