Now that I think about it, one thing I am not sure about is if self-funded students' travel/conference fees were covered. I would guess they are covered through a grant and it is just the tuition that is self funded, but I do not know for certain. Going to >1 international conference a year would be far more than the tuition.
So, I would guess it would cost ~10k/year to be fully self funded. You can recoup some of that cost working (on a student visa this is limited though), and your lab may also have an RA stipend (but this is both very low [<$20/hr] and counts towards your 28 hour/week limit).
My advice though is to never do a self-funded PhD. Being a PhD "student" is a misnomer. You are a research employee and should be compensated as such.
And while I completely agree that a PhD "Student" is a working job that should be compensated. We both know that certain doors are much easier opened when you already have a PhD. I have the financial means to help me accomplish this without taking realy much of a financial toll on it. Hence why it even remains an option.