Ant attack

[George P.]

What are the best options to rid the house of the small black ants (regular ones) infesting the property? I have caulked the cracks around the kitchen window (they always find a new way to come out), set up the baits (mostly ignored), found one or two colonies in front of the house underneath the decorative rocks and sprayed them with HomeDefence (it helped for a week or two but then they came back), sprayed the perimeter with HomeDefence....
Nothing seem to stop them. At this point the ants are finding their way to the bathroom upstairs.
Looks like I have no other options but to call the exterminator to have the TH treated. What kind of treatment will provide an ant-free life for at least a year? What cost am I looking at?
Any recommendations are appreciated.
Thank you