(Better) Translations of: 稀罕/稀奇?
稀罕 and 稀奇 are not the same thing.

The verb 稀罕 means "to value"; using it as a negative therefore express disdain. The translation given of "I don't care about your money" is quite spot on. I assume you aren't asking for a "better" translation for this.

The adjective 稀奇 means "rare", "unusual". It is not grammatically proper in Standard Chinese to use 稀奇 as a verb in the ay you did in the question, nor does it carry a connotation of disdain by itself. I'm not sure why your dictionary translated it as "be of importance" but that is clearly wrong.


  稀奇
  
  解釋: 稀少、奇特。熊貓長相稀奇，常令看過的人留下難忘的印象。
  
   -- 教育部國語辭典簡編本


Note that certain dialects (notably Sichuan but perhaps also others) do use 稀奇 as a verb. In this case the intended meaning of 稀奇 becomes "to cherish". It is however a decidedly non-standard usage.