Price, charge, cost, expense can mean what is given or asked in payment for a thing or for its use, or for services.
Price and charge in their ordinary nontechnical use commonly designate what is asked or demanded in the case of price, especially for goods or commodities; in the case of charge, especially for services.
In economics, however, price does not necessarily refer to a fixed sum of money asked by a seller, but to the quantity or number of units of one thing exchangeable in barter or sale for another thing.
Charge, especially in accounting, also applies to what is imposed on one as a financial burden.
Cost and expense in their ordinary nontechnical use apply to what is given or surrendered for something— cost often implying somewhat specifically the payment of the price asked and expense often designating the aggregate amount actually disbursed for something.
But cost sometimes replaces price with, however, a difference in connotation. Since cost applies to whatever must be given or sacrificed to obtain something, to produce something, or to attain some end whether it be money, labor, or lives or whether it is actually given or sacrificed, it, when replacing price, tends to suggest what will be taken or accepted from one in exchange rather than what the item is worth.
Expense also may denote expenditure especially but not only of money.