If you are an Amazon Prime member you can get 3 lbs. Oxi Clean and 1 lbs. TSP/90 delivered to your door for $13.44 which is $3.36 a pound for 4 lbs. That is actually cheaper than I can get it retail around here.
One of the cheapest places I can find has PBW for 20.99 plus $6.99 shipping (no HBS within 60 miles).
That's $27.98 which is $7.00 a pound for 4 lbs.