A reduction in the usual price of something.
Discount
Something sold for a price that is significantly lower than usual / lower than its value.
Bargain
Something sold at a good / reasonable price taking into consideration its quality.
Value for money
To have enough money to buy, keep or do something.
Afford
To pay back money received or spent.
Refund
A piece of paper which proves that money or goods have been bought or payed for.
Receipt
Money in the form of notes and coins.
Cash
An unnecessary or wrong use of money.
Waste
The money that is returned to someone who has paid for something that costs less than the money they gave.
Change
An occasion when goods are sold at a lower price than usual.
Sale
