SSL certificates are not available through DigitalOcean directly. You can get a free SSL certificate to use with your website or application through Let's Encrypt. Check out https://www.digitalocean.com/community/tutorials/how-to-secure-apache-with-let-s-encrypt-on-ubuntu-16-04 for a tutorial on how to get one and use it with the Apache web server software.

Edit: If you plan to use it with something else and/or don't use Ubuntu, check out their website directly: https://letsencrypt.org/getting-started/

If you want to use long term SSL for Free you can use Cloudflare Shared Free SSL services , it is free.

By "the price of SSL" I'm assuming that you mean a certificate. In that case, it depends on where you get them. You can get one for free by either:

1. Using Let's Encrypt (this tutorial if you're using Apache or this tutorial if you're using Nginx)

2. Using Cloudflare Universal SSL (See this tutorial for adding your site to Cloudflare and then this tutorial on Cloudflare's website for setting up SSL)

You can also pay for SSL from another certificate authority, such as Symantec, Comodo, or GoDaddy. Additionally, many places, such as NameCheap resell certificates from authorities like Comodo. It's only recommended that you go the route of getting a paid certificate if you're looking to get a Extended Validation Certificate, which is really only useful if you need the identity verification aspect of EV Certificates for additional security, such as if you're an online store, payment processor, bank, etc. If you're not one of those things, than I suggest getting one of the free certificates.