Crowd shopping

Hi there, I was looking for a php/MySQL/Ajax programmer with fantastic designing skills to develop A crowd shopping website. It should be a simple online store where users can buy products. The custom thing is that every time a product sale has reached the quantity-discount-margin the price will drop. For example if my supplier offers a iPod till 5 pieces for 100$ and above 5 pieces for 95$. The price should update it self to 95$ when the number of sold iPods reaches 5+. This one of the features that has to be build. All coding should be well organized and in the form of a base and build modules above it. So it will be easily to develop new products / features above the base (API ). Coder should be well experienced in the development of complex websites, installing SQL certificate and build the website pre-calculated scalability. Thank you, Vikash