The Chilean peso trades freely against the US dollar; there is no black market rate like there was until recently in Argentina.
The peso has dropped in value dramatically against the US dollar over the last couple of years, due mainly to the commodities crisis (the price of copper, Chile's main export, has plummeted). I suspect the website you cite has simply not been updated recently.
Foreign tourists are exempt from paying the 19% VAT (it's called IVA in Chile) on hotel bills. When you check in, they will ask for your passport and will make a photocopy of the passport and the tourist card that you will receive from immigration authorities at the Santiago airport on arrival. When you check out, they will bill you via a "factura de exportación" which does not include the 19% IVA.
It has been a while since I paid a bill with a factura de exportación, as I was until recently a resident of Chile and therefore had to pay the IVA. But if I recall correctly, the bill will be in US dollars. You should clarify this when you check in, and if you will be billed in US dollars you should clarify the exchange rate that the hotel will apply. Current exchange rate is approximately US$1.00 = CLP$715. At that rate Chile is a great travel bargain!