If you rent for a day it can cost you silly money (although not usually as silly as 70 unless you rent directly in a resort). However, shop around and rent for a season and you should be able to find a board and binding for 250 or so. And that will be a lot better quality than anything you can find second hand for the same money. Plus if you buy second hand you are going to have to get the board serviced which will cost another ~50.

Plus boards don't last forever. My oldest usually manages to get through one per season (which is why he only rents these days). Admittedly his style is fairly extreme....