Thoughts:
First thought - Woo Hoo Mark is making a MODX conference!
Pricing - I agree with the notion of having conference ticket prices separate from accommodation costs -- some people may be traveling with a spouse or friend and/or tacking on a vacation afterwards (I know that's where my brain is headed right now.)
I think it would be hard to get a registration fee up front without having most of the details -- including price -- already hammered out. I probably wouldn't commit to a conference without knowing what my bottom line will be.
As an example, I just paid about $400 to attend a really high-quality 2-day conference here, Artifact East in Providence. I feel that price is a bargain. Most conferences here in the US that I would be interested in attending are more like $400-$500 per DAY. I would not pay much more than that. The full-day workshop following Artifact conference was $500 (I didn't attend). I understand it was a higher price because attendance was limited for the workshop so that people could really participate and get individualized attention from the workshop leader. Seems worth it, but beyond my budget.
Maybe you could figure on a certain amount of sponsorship revenue, using a very low estimation, and then whatever you get beyond that use for the after parties and pampering your speakers. And swag for attendees.
Or sock it away for the next year so you don't have to go through this again?
Content - I'd love to have some hands on workshops where we work through things like snippet creation and the stuff Susan mentions above.
Calendar - I have heard the 2014 MODXpo will be in the US of A. If that is so I will pretty much definitely be going... So, it might be hard for US residents to attend both, but maybe you're not really counting on Yanks traveling to your conference? If you do want us - please make sure your dates aren't too close to the MODXpo dates. (I don't know when it is or if a date is even set.)