What is the cost of putting
a shopping cart on my website?
There is no simple answer to this question. If you only have a few items to sell, you can probably get by with simple PayPal "Buy Now" buttons that cost very little to set up and maintain.
A full shopping cart with the ability to accept credit cards is much more expensive to set up and maintain.
We can discuss the options once I know how many items you want to sell, how you want to ship your products, how you intend to get paid, and what you are trying to accomplish in general.