late replying i know mate, but theres lots to take into account as Simon says.
e.g.
is it a solid colour wrap?
a digital printed wrap?
is it long term or short. e.g. laminated?
is your customer providing the sized and ready to print artwork
or are you? (this alone can lead to many hours labour alone).
How many metres of media will be used to cover the vehicle in hand….
those are just some important factors you need to take into account when pricing wraps. i know you are just giving the customer a quick price, but i find that’s what "they all ask" when it comes to wraps. then want you to commit to the guestimate once they have shopped around.