WooCommerce is a WordPress plugin, which means you'll need to take care of web hosting, upgrades and security. The upside is that you get total freedom and you can customize it to your liking with the help of add-ons.
The plugin is free and open source, but you will need to pay for web hosting and probably some add-ons, although there are plenty of free ones also.
The only fees you'll pay are for the payment gateway (Paypal, Stripe, etc). Since you manage hosting, you also need to take care of backups, but you have control over your data, which can't be said for most of the other builders on this list.
If you don't mind tweaking code and handling hosting by yourself WooCommerce is a very strong candidate. Otherwise stick with something like Shopify or Squarespace.