It depends entirely on the car you have. I got my IS200 done and the price should have been £200 because he had to take the back seats and parcel shelf out to get to the rear window. however as he is one of my mates uncles he did it for £180 and he is the number one person in the north west. similary he did my mates 3 door 2005 astra and charged £150 because its an easier job and requires less film.
Between £150 and £200 is a guid price although havinbg had two cars tinted now i would suggest payin the bit more to get a proper professional job.