Let me try and spell it out in words that you might understand...
People lazy.
Herbs pain to get.
Means less people gathering them.
Means price goes up.
herbs needed for potions/flasks,
herbs expensive means flasks expensive.
So far so good?
The people that are willing to herb are selling them for the prices people will pay.
Now, if you disagree you are going to have to tell me what part you disagree with.