While we sell some themes on WordPress.com, those purchases can’t be transferred to a self-hosted WordPress site. The main reason is because WordPress.com is a service (you don’t get any files to download) and the code is different to some extent. However, you can ask for a refund from WordPress.com within 30 days from your purchase and buy the self-hosted version of the theme from our shop.
To have a better understanding about the difference between these two platforms, we recommend you to read this article. This way, you can choose wisely the right theme for what you want to accomplish.