It's not cheap, and our government doesn't welcome foreign permanent retirees. In fact it puts obstacles in their way, mainly financial ones. They are required to buy a residence for $750,000 and have certain annual income of $150,000. Ridiculous! However, foreigners (whether retired or not) can buy houses or apartments here for a lot less than $750K, and live in them for months at a time. They just can't become formally domiciled here, or become citizens.
I'm retired, and we live modestly on what my wife earns. (I used to work here, so don't fall under the standard rules for retirees.) We don't operate on a proper financial budget in our house, but I would say our annual expenditure is in the region of US$50,000, not counting vacations. There is no Income Tax or Property Tax. But there is import duty on everything, so prices are quite a bit higher than in the US or Canada.
A few essays on this subject can be found on my personal blog (see profile) in February ("Retirement worries") and March ("Investing for retirement" and "Gold, and other currencies"). They were written for residents of Cayman, but their content is relevant to all retirees anywhere, really.