As you've noted, headstamped 7 WSM brass is rare and expensive. You'd need around 200-250 cases to get through a barrel. I think you could finangle that on Gunbroker for ~ $500-600.
Jeff, Olin just did a run of 7mm WSM brass last month. I picked up 3 bags locally for Dober at $40 a bag. Cabela's had it in stock for a while too at that price.
