I know UK is not your market, but here is a comparison of the first two grocery store own-brand saags I found:
£1.65/$2 - https://groceries.morrisons.com/webshop/product/Morrisons-Th...
£2/$2.43 - https://www.tesco.com/groceries/en-GB/products/293944759
Perhaps you don't get as much protein with these though.
(Incidentally why is everything obsessed with protein these days? Seems like every food you buy now says "source of protein!" Or "contains protein!)