The answer is enormously variable. There are cruisers that live without refrigeration on 25ft makeshift boats and I know of one that did so on a 60ft Gunboat catamaran with absolutely every luxury.
As general rule, $50k per year would be a nice budget, assuming none is taken up by a mortgage and its all cruising money. However, no way you can count on making $50k per year on $800k in this economy. If you start stealing principal early, it makes it even more difficult to catch up later.
Still, you have a nice nest egg.
Do your own budget.
Boat insurance (research this to be sure you can get it at all)
Boat maintenance (you will be hard on her, so plan more than current experience)
Foreign country immigration fees (research here http://www.noonsite.com
Travel home costs (most fly home for a holiday or respite)
Communication (email, cell phones, whatever)
If you are going to do this for an extend period, expect to budget upgrades in laptops, chartplotters, whatever. Can you imagine still sailing with the same stuff you had 15 years ago?
Best of luck....... Enjoy the cruise.