jCommerce is an online shop system that offers a wide range of out-of-the-box features that allows online stores to be setup fairly quickly with ease, and is available for low price.

Full Feature List: http://extensions.soft-php.com/jcommerce.html
Demo Site: http://demos.soft-php.com/jcommerce/

Package Includes

Joomla component for osCommerce 2.3.x (compatible with Joomla! 3.x and 4.x)
15+ Modules and Plugins

Features

Easy installer, one-click upgrades
Works with Jquery,Mootools,Prototype(No conflict mode)
Works with most of the joomla templates.
Manage osCommerce configuration and osCommerce users from Joomla admin panel
osCommerce interface displays into native Joomla! content
General Functionality
Setup / Installation
Design / Layout
Administration / Backend Functionality
Customer / Frontend Functionality
Product Functionality
Payment Functionality
Shipping Functionality
Joomla Admin Panel
Combined with Joomla template's CSS
Frequent Upgrades and Good Support.
No encoding loader needed
Works with existing and new extensions(payments,modules) of osCommerce.
No iframe used.
Unlimited Installation
Unlimited domain
GNU/GPL license  http://www.gnu.org/copyleft/gpl.html

Minimum requirements

Joomla! 3.x, 4.x
PHP-module curl active
PHP-module simple xml active
PHP-module json active