I hadn't the faintest notion of what she was talking about.

This is probably because nobody has the faintest notion about costs.

"I haven't the faintest notion how to get into these things."

She had not the faintest notion how to get her own clay piece started.

I had no faintest notion what he was figuring out.

But then she got a faint notion, and began to understand.

But that first day at the laboratory, I didn't have the faintest notion of what had happened.

From looking at him no one could have got the faintest notion how to bet.

What the Russian was actually saying, no one present had the faintest notion.

He didn't have the faintest notion what the man was talking about.