Dropdown for product price based on category of product

Hi, my client has a request to provide a fixed set of pricing based on the category of the product. e.g:

Games: £20
CDs: £10
DVDs: £7
BlueRay: £25

Is this possible with MarketPress and if not could someone point me in the right direction for how to customise the page (wp-admin/post-new.php?post_type=product) Due to the url-rewriting I don't know where to look to find the add product page.

Thanks

Adam