Pay attention to the difference between these 2 words. Basically, everything is different about them – spelling, pronunciation and meaning, but students (especially beginners) still find it difficult to make a proper distinction between them.
COAST /kəʊst/ – the part of the land near the sea
COST /kɒst/ – how much money something is worth/you are required to pay for something
So… How much does a house on the south COAST of France COST? :-)