> They are obligated by law to do what they said they would, even at their cost, if above and beyond what they expected and not covered by the contact as a cost

> They are obligated by law to do what they said they would, even at their cost, if above and beyond what they expected and not covered by the contact as a cost-plus, or risk losing their contractors license and being civilly liable. At least in the vast majority of US jurisdictions. This is technically true, but misleading. They have to follow the contract, but the contract likely includes exceptions for unforseen issues. And while you can technically sue a contractor for breach of contract the only reason to do so in this situation would be spite. The rational choice if a contractor cheats you on a small project is to be sad and move on. (Google around and you'll find lots of people who learned that the hard way).