Right now (through 12-13) HEB has this yellow B coupon making the Post Pebbles 3 for $5.  Since this is a B coupon, you can combine it with the manufacturer coupons in the 11-6 SS for $1/2.

See the deal plan below:

Buy 6 boxes $10 after 2 Yellow B coupons
– 3 $1/2 inserts
=$7 or $1.17 a box