Protip: always use plus aliases when signing up for things like this. Use a unique plus alias for everything you sign up for (the convention I use is e.g myemail+yourcompanyname@mydomain.com). This convention lets you be sure exactly who sold your info when the spam comes, based on the to address, and it also lets you easily block email from that source after you've got your tickets.

The only downsides are that sometimes it doesn't work if their shitty form verification insists that the plus character isn't valid in an email address. In those cases I tend to set up an actual mail alias (yourcompany@mydomain.com), but that's an annoying extra step - pluis aliasing is simple, requires no configuration, and works everywhere. But this is pretty rare. And if you're using it to sign in to things, you'll want a password manager so that you can remember what plus alias you used for each site.

Don't misunderstand me - I'm not defending the behaviour you're posting about - it's reprehensible and I wouldn't have bought tickets at all under such a system. What I'm offering is a way to make it more manageable for people who don't want to go without things that you can only buy under these user-hostile models.