I'm not sure of your employment status, but if you are an employee somewhere, it's quite possible that you can get your employer to at least partially pay your way.

The cost is an interesting thing to attempt to justify, and it depends entirely upon how you take on the conference. If you simply attend, sit in the audience, and listen to some of the talks, with rare exceptions I would argue that the cost isn't worth it for any conference. You'll notice that many conferences put videos of their talks online–for free. There's a reason for this: the talks are not the most valuable aspect of the conference; rather, the rest of the experience at the conference is the precious part.

This isn't to say that the talks are unimportant. The quality of speakers reflects on the quality of the conference as a whole and the speakers set the stage for the great discussion that will flow from there. At a conference, you'll sit in the audience and listen to some really intelligent person speak about a given topic, and people really get into what that person has to say; but the real magic comes just after the speaker finishes. You'll notice that those that really found the talk interesting will rise from their seats and rush to the stage, crowding around the speaker to engage her in discussion. Fellow attendees–speakers or otherwise–will further break off into their own groups to keep the conversation flowing.

So, if you think of a conference as a novel, then imagine the speakers as the main characters. While they keep the plot flowing, it's really the other characters–the attendees–that tie everything together and make the main characters worthwhile.

Additionally, you'll find yourself thrown into a large group of people where you are both stronger than others in some areas and weaker than other attendees in different areas. This tends to be any geek's best dream–you're simultaneously around people from whom you can learn and to whom you can impart knowledge, which means that you're in an environment that fosters creativity and open discussion.

You won't remember everything that you learn at a conference. That isn't the point. Instead, you'll be introduced to a wide range of new ideas, and you'll take that new perspective back to work or other areas of your life and apply it accordingly. For example, I saw Nathan Marz's talk at Strange Loop 2011, where he open-sourced Storm. For days after (and, frankly, even as I was working on something just the other day), ideas that he put forth in that talk have resonated in my mind, and I've architected solutions to numerous problems in ways that I otherwise would not have imagined, all because I was exposed to a different point of view.

This benefit is what just one speaker has done for me–now imagine how powerful this is when you're exposed to 20, 40, or even 60 different speakers! The benefit continues to grow as you talk not just with speakers, but with fellow attendees as well, absorbing their newly gained snippets of knowledge and sharing some bits of your own.

For these reasons I would say that, while $450 can indeed be a lot of money, it isn't just applied to the two days that you will be at a conference. Instead, it continues to work for you through the lessons learned and–perhaps even more importantly–people met.