WooCommerce

WooCommerce is a free, open-source plugin that transforms WordPress into a fully-functional e-commerce store. Its greatest strength is deep integration with the world's most popular CMS, making it ideal for content-driven sites and blogs adding commerce. It offers immense flexibility through thousands of themes and extensions. Users have full control over data, hosting, and costs, but are responsible for security, performance, and updates.

The initial cost is low, but advanced features and extensions add up. It's best for WordPress-savvy users, developers, or businesses that prioritize content marketing alongside sales and want complete ownership.