IIS 7 and Above
IIS 8.0 and Website hosting
Re: IIS 8.0 and Website hosting
Feb 15, 2019 10:00 PM|lextm|LINK
You can use URL Rewrite module to redirect all users from old URLs to new ones. However, you cannot prevent them from visiting the old URLs (if they saved bookmarks and so on).
If you do want to cut cost, you have to stop support the old site and explicitly break those users. Is Let's Encrypt an option for you? They provide free certificates.