Twinjector full-unit with two 4-ounce injectors is $159.
Buying the kit and two 6-ounce injectors is $199.
4-ounce injector is $49.
6-ounce injector is $59, only $10 more than the 4-ounce injector...but buying the kit and two 6-ounce injectors is $40 more than the existing twinjector full-unit.