OP you should listen to Ghost6 and ignore most other posters because there is some seriously delusional stuff being posted in this thread (I'm looking at you janjanmmm, with your "academics work 6-8 hours a week and get $120k/year on average").
Most of what Ghost6 says is basically right; doing an unfunded PhD is likely to be a bad decision - if you are paying both tuition fees and living costs then youre looking at something like £40k+ debt to get a degree which has very low earning potential outside of a few subjects, and few career options unless you are at a top place. The average academic certainly does not earn $120k/year; below professor level in the UK a salary in the £40-55k range will be typical, although some fields will let you supplement that with consultancy. In the US its around $70-120k in most fields; econ tends to be higher but still unlikely to be over $200k unless youre in finance. In any case, you really dont want to be servicing a £40k+ debt on that kind of income. You can argue all you like about whether unfunded people are 'worthy' of the PhD, but it doesnt make financial sense unless you are indepenently wealthy.
I guess there are some exceptions like if youre in an area that has high earning private sector options (eg econ/compsci/statistics) and your unfunded offer is from a top place (which in this context basically just means Oxbridge and 1-2 others), but even then I would make sure you have seriously considered what you're getting into.