Drysuits and the associated undies do rack up the costs. Whilst you can use a cheapo drysuit, you soon find their limitations especially in the summer to winter transition.I think it depends more on how often you dive, not where you dive I agree that "vacation" divers-- like one/two trips a year-- maybe it pays to rent. Any more than that and you're better off financially to buy everything and rent only tanks when travelling (assuming you don't live where it's warm). Due to the small amount of weight needed in the tropics, I usually bring my own as well. Plus, with such things as a regulator, it's nice to always have your own.
I dive here 6 months in my wetsuit and very sparingly in the winter (20 minute dives). Never owned a drysuit, but it would be nice.
A decent drysuit's a lot of money, $2000 plus. That's most definitely an investment in comfort and you need to be pretty addicted to diving by then!