1.  Because they know we all like playing football .We will look on the football as an expensive present and keep it well.

2.  This pair of playing cards were very expensive.

3.  to make fresh water from sea water is so expensive that many countries can't do it.

4.  Another way is to use the fresh water for a second time, but it is too expensive for us.

5.  You know, in Great desert, fresh water is more expensive than gold.

6.  And turn sea water into fresh water is very expensive, so people can't make the use of sea water.

7.  On the one hand , the card is more and more expensive, people need a lot of money so that we sometimes can't afford them .

8.  Buying a TV set is more expensive than buying newspapers.

9.  Greeting cards are so expensive that we have to spend much money on them.

10.  So it is waste of money to buy expensive cards and it is unfit to bother the postmen.