Help with "I would like some dollars"?

Question:

In my Pimsleur lesson today I had to say I would like some dollars please I said

ドルをほしいんですが

the actual correct answer was

ドルがほしいんですが

what is the meaning of what I originally said? I would like to try and understand what I said that was wrong.

Thanks :)

Answer:

（わたしは）ドルがほしいんです
This is a simple "S + O + V" sentence, but when we say すきだ、ほしい、（verb）～たい
we just don't use を (which is usually placed as an object mark, right?) and use が

Don't ask me why.... let's say that's one of mysteries commonly seen in every language.

---------- Edit:
↓Yep, （verb）～たい: この映画が見たい。 おもしろい本が読みたい。
（While we say ；この映画を見に行った。　おもしろい本を見つけた。）