I think e-mail is a `cheaper and quicker way than a letter这句话对不？

不对 应该是
I think e-mail is a cheaper and quicker way，compared to a letter.
或者
I think e-mail is cheaper and quicker than a letter.

不对

I think sending e-mail is a `cheaper and quicker way than sending a letter

我认为电子邮件比信函更便宜、更快捷。

对
我认为电子邮件是一更廉宜而且更快的方法超过一封信