394820 Shopping Cart Software

We are looking for someone to build some software for us similar to that of Mercantec ([login to view URL])Ecommerce Express. We are in exploration mode for what it would cost to build such a system which allows a user to plug information about what they want to sell etc, then the user then gets given snippets which they can paste into their website. The full functionality can be seen at [login to view URL] you will need to create your own user name and password - it is free. Other requirements: 1. multiple user accounts 2. linked to paypal 3. must have Australian Dollars linked in it 4. must be user friendly and follow the same format and functionality as Mercantec Ecommerce Express.