Ok.. I gotta correct this.. Let's revisit the math here...
You figure out how much you save by doing: (Price Paid) / (MSRP Value)
B1G1 50% off = (60 + 30) / (60 + 60) = 3/4 MSRP -> 25% off
B2G1 free = (60 + 60) / (60 + 60 + 60) = 2/3 MSRP -> 33% off
If you expand this out to the lowest...