To be clear, there are many options available, most of which will run a minimum of $500 for decent work. osCommerce is just one of the better known solutions.

My recommendation as to which cart/commerce solution best suits you can only be made with a more in depth project description. Shopify and Xcart are two other very valid options to consider; my personal suggestion being shopify.

Regardless of who you choose to set you up, I'm always happy to give my opinion as to the best option for your situation.