I don't see any problem with charging US$800 for a conference ticket. I don't think I've been to any conferences for less than that apart from WordCamp's. I however see a problem in that they're competing directly with WordCamp's who are obviously much cheaper. And even though they're providing support to get the speakers there, I don't see that making a huge dent in the quality of those speakers. The best (WordPress) speakers already do lots of presentations for free anyway.

One bonus I do see of paying US$800 is that they'll hopefully get very good food. I've been to a few WordCamp's which provided truly awful food. They're mostly good, but I've come across a couple of shockers where I ended up going to grab a bite down the road instead of eating the free food on offer ;) But quite frankly, I'm not willing to spend US$750 for a few meals, no matter how nice they may be!

So my opinion in a nutshell ... it's most definitely not a rip-off, but I wouldn't go simply because I can't see any real value beyond what you can get for (almost) free at a good WordCamp.