Costain is a historic English surname that has been used by a number of individuals and companies over the years. Unfortunately, there are not many synonyms for the word "Costain," as it is a unique name. However, if we are speaking more generally about cost or expenses, some synonyms could include expenditure, outlay, budget, charge, or expense. These words all refer to the amount of money or resources required to complete a particular task or project. Whether you are planning a large-scale construction project or simply trying to balance your personal budget, it's important to keep track of your costs and expenses to stay on track financially.