What is a fair price to integrate shopping cart?

[antmay]

Hi,
Can anyone tell me what is a fair price to integrate a shopping cart into an existing site?

When a shopping cart is said to be template-based, does it mean....
I can change the color of the checkout page?
I can add my own logo to the checkout page?
I can control the placement of the member login in?

Any suggestion on the shopping cart with the above requirement will be greatly appreciated.

Thanks,
Anthony