I requested a pack of these AA's for Xmas so if I get them I will post back here.
Ion-Core AAs are 2x 4-pk for $12.50 + free shipping on eBay - that's $6.25/4-pk
(no tax, no gas either)
prob cheaper than a single 4-pack in a local brick & mortar shop....
Just search for "Duracell propay" on fleaBay,
(no affiliation with the listing or vendor)
then do due diligence on photos and description, before parting with money.
I got my Ion-Core AA in post #52