The phrase "extra cost" refers to any additional expenses that are incurred beyond what is considered standard or expected. This can include charges for services, goods, or fees that are not included in a regular price or estimate. The term can be used broadly to refer to any unexpected or unplanned costs, such as surprise bills or hidden fees. In general, "extra cost" refers to anything that requires an additional outlay of money beyond what is already budgeted for or anticipated.