I have a local shop selling rounds for approximately $1.60/round or thereabouts, all from boutique factories (I did get a couple boxes of Sellier & Beloit).

Any leads on where I can not spend $60+ on 40 rounds of .300 blackout? No can so I'm buying supers currently.

ammoseek.com
Search every morning. Expect that it may take days -- even weeks -- to find what you want.

sgammo.com for a single source

I haven't purchased pistol or rifle ammo locally in many years. High-volume shotgun ammo for clays can often be purchased locally for less, due to shipping costs.