That is expensive, this is slightly cheaper.
那个 很 贵，这个 便宜 一点。
Could you give it to me a bit cheaper?
你 能 不能 给 我 便宜？
This really isn't cheap.
这个 真 不 便宜。
It is too expensive. I don't want (it).
太 贵 了，我 不 要 了。
This is too expensive.
这个 太 贵 了。
This is more expensive than that.
这个 比 那个 贵。