Price OF this book or Price FOR this book?

Hi there, when i am buying a book from a seller, do u say can you please quote me the lowest price of this book or for this book?

and can you guys please give me the reason behind it?
Thank You.

Can you please quote me the lowest price (that you are willing to accept) for this book.

You pay for a book, you accept payment for a book. ‘Of’ is the wrong preposition.

Some other points to avoid sloppy writing:
When you write the pronoun ‘i’, it should always be written as a capital letter,
Sentences always begin with a capital letter.
There is no such word as ‘u’, you should write ‘you’.
The phrase ‘thank you’ does not need to be capitalised. (The only reason ‘t’ is capitalised in your case is because it starts a sentence.)
If you are going to use direct speech, it needs to be punctuated to separate it from the rest of the sentence.

This is how your message should have been written:
Hi there,
When I am buying a book from a seller, do I say, “Can you please quote me the lowest price of this book?” or is it “…for this book?”
Also, can you please give me the reason behind it?
Thank you.