I have lived in Peshawar for months at a time. One of my uncles is a native of Peshawar. One of my bhabee (May Allah grant her Jannat. Ameen) was his daughter. She practically raised me. So I have first hand information.
I have dug out an online resource for you to refer too.
Unison of Another Kind :: Khyber.ORG
An excerpt from this article:
The custom of buying brides is rooted in the tribal area’s culture and the bride-money has risen sharply because tribesmen gainfully employed in the Gulf States are able to offer a higher price for the girls of marriageable age. In comparison, girls could be bought much cheaper from peasant families settled in districts such as Mardan, Charsadda, Swat and Malakand Agency. Husbands and families paying huge amounts of money for girls often consider them as some kind of property instead of wives and treat them accordingly.