What makes the Singularity Summit so much more expensive than all these other events?

Singularity Institute learns new things every year about cutting expenses from putting on a major conference, but we know enough that we're now heading into the 6th annual Singularity Summit and can attract big-name speakers. Why does it cost more? There isn't yet much corporate sponsorship or paid booths, as at Comic-Con, though we're working on that as we go into the future. And we have higher profile speakers than Intervention or NECSS. But I certainly want to talk to the people who put together NECSS; thanks for providing the link.