clarifying cleanser shampoo

This is a life saver! I have an oily scalp and had to wash my hair every 2 days, it looked lank even after 1 day. When I washed my hair there was tons of it in the plughole. It would grow back but...

so I'm at TJ Maxx and I see this shampoo on clearance for $16 for 33 ounces. The retail price is $42. Who knows. I wash my hair maybe 3 times a week depending and am so sure I have lots of product...