Bob,
Not familiar with the job of purchasing people., but you just remind me of something.
I remember that my company (ASME S&PP stamp holder) once used an A material for an ASME project. The A material met all requirements of the relative SA specification. The MTR from the material supplier certified its compliance to the A Spec. but not to the SA one. Then got ideas from our AI that as an S stamp holder, my company has been authorized by the Society to certify that A material to the SA Sepc.. All we needed to do was to verify all the SA requirements were met and made a supplementary statement on the MTR for the SA compliance. Our Data Report can then directly indicate the SA spec.
Maybe that is why they call it "Certification of Authorization".
From this point I donot see the SA cost more. Either I donot see any qualification requirement from ASME Code books for the material supplier, or is there any?
Of course, not all the SA specifications completely equal to the relative A ones. If the SA one is tighter or have additional requirements, the supplier will have to spend more money meeting the SA requirement and hence you will need to pay more.
Thanks,
Jovi