EXPENSIVE
(TO BE)

guì
CHEAP
便宜
piányì

How come (it is) so expensive?
怎么 那么 贵?
Zěnme nàme guì?
This is 20kuai more expensive than that.
这个 比 那个 贵 20 块。
<Zhège bǐ nàge guì 20 kuài.>
The more people are there, the more expensive the stuff is.
人 越 多 东西 越 贵。
Rén yuè duō dōngxi yuè guì.
Going by plane is faster but more expensive.
坐 飞机 快 可是 贵。
Zuò fēijī kuài kěshì guì.
Could you give it to me a bit cheaper?
你 能 不能 给 我 便宜?
Nǐ néng bùnéng gěi wǒ piányi?
Is the clothes, that you are wearing, expensive?
你 今天 穿 的 衣服 贵 吗?
Nǐ jīntiān chuān de yīfu guì ma?