This will vary from dentist to dentist and is dependent largely on the fee charged by the dental laboratory who make the veneers. A higher price will often go hand in hand with better materials and a high degree of skill from the technician, which all adds up to the best cosmetic result.
The price is normally per tooth, but the greater the number of veneers you have, the lower the cost per tooth is likely to be - bulk buying if you like!
A typical amount would be anywhere from £150-£250 per tooth, but possibly higher in some areas.
If there is a true clinical need for a veneer (that is, it is not simply to improve the appearance of the tooth - such as a malformation in the enamel covering the teeth) a veneer may be available on the NHS. If you have to pay NHS charges, this will currently cost you £194, including any other necessary treatment. But be warned, remuneration for dentists for this procedure is not high which affects how much we ca afford to pay the lab who make the veneer. In short, even if you can convince a dentist to do it on the NHS, you won't get the best quality material, or even necessarily a great colour match.
I am a dentist. I currently charge £200 per tooth for porcelain veneers.