Buy (3) ............ get $2.00 "Post" cat + -NO- "Kraft" cat = total of $2.00 (ie $0.66/box savings)
Buy (4) ................. $3.00 "Post" cat + $2.00 "Kraft" cat = total of $5.00 (ie $1.25/box savings)
Buy (5) ................. $4.00 "Post" cat + $3.00 "Kraft" cat = total of $7.00 (ie $1.40/box savings)
Buy (6) or more....... $4.00 "Post" cat + $4.00 "Kraft" cat = total of $8.00 (ie $1.33/box savings)

Above works if you purchase ANY combination of the following 4 varieties (10oz or larger):

Post Honeycomb cereal
Post Fruity Pebbles cereal
Post Cocoa Pebbles cereal
Post Bamm Bamm Berry Pebbles cereal