The bait system is to allow the termite take the bait/food to the nest and allow the queen and colony to eat the food. It will stop the reproductive system so the termite colony system will die.

After it die the smell still around this make the other colony don't overtake the area.

I heard this can last up to 10 years or more.

Depend you need to do the chemical treatment of the bait system. Bait are more expensive.

Last time when i ask for my mom house, is about 3.5k for bait system. Chemical is cheaper, around 1k to 1.3k, but it will drill and pour the chemical. It drill on all your floor including living room floor, then spray the chemical on the roof too. Btw they use the similar chemical you can get on the h/w shop.