Let's say we have 40 employees who code and 30 employees who create tickets, and we want to get all of the security scanning features that the platform has to offer.
For GitLab, we need the $99/user/month plan because the security features are only available in that subscription. Guest users are completely free, but they're extremely gimped when it comes to issues, so most likely you'll have to have most if not all of your non-coding employees at the $99/user/month tier. Final price is $6930/month (or $3960/month if you can really handle the gimped guests).
For GitHub, you need to pay $19.25/user/month plan for every user and $49/month for every person that commits code for the security features. So that's $1347.50/month for user accounts and $1960 for security features for a total of $3307.50/month.
GitHub is not even half what GitLab wants. It's even less than the gimped guest user experience that you can subject yourself to with GitLab.