Stock up?
Last I looked...HSM was the only place to get WSSM brass with Federal head stamps and they have been out for some time. I believe the last few thousand pieces from them, were bought up by one person, and he's poaching them on GunBroker.
However...when the supply is gone, that's really your best bet. Pay to play and plan ahead next time.
I had, and loved my 243 WSSM and a fella made me an offer I couldn't pass up. I let mine go just in time, because for 1.50/ea for brass...I would just let it sit in the safe.
HSM WAS selling it for .71/ea when their supply was ample and even that was high...but available.
I don't think I ever paid more than .45/ea and most of it was around .37-.38