You can get rooms at the Four Seasons for much less (
I think that now would be a good idea to find out how much interest in attending there's going to be at various price points.  Some people will be able to attend no matter what the cost, but for many others there's going to be a ceiling above which it's simply not affordable.  In deciding where to hold the event, you need to consider whether you want it to be more of an industry insider event for people who are happy to drop a couple of thousand dollars on attending or whether you want it to be more accessible to the average Bitcoin user.