Early on I would actually take vacation and spend my own money to attend. I think this all depends on your employer, and for me I was privileged enough to be able to do and afford this.
I can say for sure that it was one of the best decisions I have made. The connections I made, the people who influenced me, the energy that I took in at these events are had one of the biggest impacts on my career.
I think early on, and depending on your employer, it may be hard to find an employer that embraces and supports people attending events. I would say that as your career progresses, do your best to find companies that support this and will pay your way to at least one event a year if that is what interests you.