The PrestaShop platform itself is completely free to download and use. However, just the platform itself can’t help you publish your website on the internet. You can use it to design your website and add products to it, but to make it go live, you need hosting and a domain name. Both of which cost money.
The PrestaShop marketplace also has thousands of free and paid templates and modules. There are modules and templates developed by the PrestaShop team, along with those developed by third-party companies.