ChatGPT 4 charge me more expensive

I implemented ChatGPT 4 Api to my site to help detect the text both in the edit fields and the documents submitted by our members.
I have realized that the price we are charged each time is way more higher than your standard pricing chart.
Can you please find out what’s wrong with it? For 2240 tokens it’s charging me $0.18 and it looks like each different time it’s not charging using the same standard.
I also have some questions with ChatGPT 4o:

  1. Can it input pdf files with both text and photos?
  2. Besides input the text in the photo, can it detect sensitive content within the image? For example: porno, political, nude, criminal etc?