1 DIY roach killers cost as little as $5 to $15 (for a can of kill-on-contact insecticide, roach foggers, or bait traps) and as much as $50 to $60 per gallon for spray products that claim to provide 12-month roach control.ew pests produce the feelings of disgust that cockroaches do. You shouldn’t, however, let these primordial pests work you into a state of all-out chemical warfare. The same substances that are used to kill roaches can be hazardous to the health of humans and pets.