According to mbstone's post, it's $15 per day per device. Unless someone else posts conflicting first-hand information, I'll believe this is the case.
So if you have two devices you want to use for one day, it'll cost $30. Or if you have one device you'd like to use for two days, it'll also cost $30. Or you can pay $20 for the daily resort fee which includes all devices, which may or may not be a better deal.

But options are good.