Summer Schools and academic career
I'm a PhD student in my final months, I'm in a different field (geophysics), but I've been to some summer-schools that I found very valuable.  One lecturer even stated that summer schools are the best forum for scientific exchange.  The summer schools I've been to didn't have as many participants as yours, but still, besides from the obvious point of acquiring knowledge and skills, summer school permit you to:


Meet and talk to senior people in your field
Meet other students, who may be going to be the future senior people in your field


The bottom line is: A summer school is as good as its lecturers are.  Look at the list of lecturers, and ask a senior scientist you know to look at the list.  Are there many famous names?  Go for it.  Are those mainly lecturers who spend most of their time teaching at not so well known institutes?  Then you can probably spend your time and money better elsewhere.  Depending on what's included (lodging/meals/...) and on how long it takes, 1000$ is not bad, although of course it's better if you can find someone else to pay it for you ;).