The cost of the actual chlorine per oz is:

Cost/Oz CL = Price / (Jug oz * Concentration)

so for each of those

$1.99 / (128 *0.06) = $0.26/oz
$2.49 / (128 *0.0825) = $0.24/oz <-- Best Deal
$3.75 / (128 *0.10) = $0.29/oz

This will work for non-standard jug sizes too.