Construction of a Groupbuying marketplace

Hi there, I have an Amazon clone, however, I would like to either have further development on this clone (additional features/functionality) or have a site constructed from scratch. My concept must achieve the following; 1) I want to retain the whole marketplace/multi-vendor element as this forms a major part of what I require, however, I would like to overlay onto this marketplace a group buying system (not a daily deal site) that will enable front end users to effectively register their want of a particular product and purchase their item in a coordinated manner with others thus reducing the RRP price that was displayed initially. 2) This group buying feature will exist for all products that any merchant/seller lists with our site and these group buys will remain active for a specified period in which users can enter and exit at their discretion until the specified window expires (this list will automatically reset depending on the seller/merchant’s wishes). Users will be able to view the real-time price of a product relative to the number of participants that have registered their wish for that particular item (this will work using real-time sliding scale discounts). Once this window has expired, payment will be taken using credit card details/paypal. 3) There will be a blogging/social network element to the site in which users will be able to set up accounts and add friends to their own circle categories. This will allow automatic communication with other user types that may be interested in purchasing the same item (based upon previous purchase history and those whom have been added to a particular users circle) alerting others that they can enter the group buy and thus enable them to buy at the new lower price. 4) There will be effective features that provide incentives for users to refer a group buys, promote and use the site: for instance a referral reward scheme, additional default discounts, loyalty pricing, group buy suggestions, registration rewards etc… 5) Merchants/sellers must be able to upload their listings in bulk via an easy to use CSV importer. Sites that may provide an insight into what I am trying to achieve can be obtained from the following websites: [login to view URL] [login to view URL] [login to view URL] I require a time frame for when this project can be completed, the price of this project and any other relevant details thank you. I will look forward to your correspondence. Kind regards