Hilton Hhonors is offering a 50% discount on the purchase of points up to 16th September. All you have to do is log into your Hilton Hhonors account to see the discount.
You can purchase up to 80,000 points at a go, at a cost of USD$400, meaning each point will cost only USD$0.005. They have had this promotion a couple of times this year already and is extremely lucrative if you have a trip coming up soon where you have a stay in a Hilton property.
To put things into context, if one stays at a Category 1 Hotel, a night will only cost USD$25/night, a Category 2 Hotel will cost USD$50/night and a Category 10 Hotel will cost USD$475/night.
Usually it does not make financial sense to redeem for properties within the Category 3-8 range, cause you would be better off paying rack rates but YMMV.
I had the pleasure of staying at the Hilton Garden Inn Bali Ngurah Rai Airport which is a Category 1 Hotel where rates cost upwards of USD$80/night. Another notable property where one can get the most bang for your buck would be the Doubletree by Hilton Kuala Lumpur. A night would cost 10,000 points or USD$50/night, while paid rates are upwards of RM544++ ~ USD$135++.
Visited the property recently and they were extremely hospitable. Elite recognition was excellent and I was promptly upgraded to a Executive Deluxe Suite on the 33rd floor with a view of the Petronas Twin Tower. Lounge offering was awesome, the breakfast spread was huge and best of all they provided me with tons of Perrier water (I am obsessed with sparkling water). Definitely one of the best DoubleTree property I have visited in the world. Review of the hotel will be left for next time.
On the other end of the spectrum, there are the Category 10 Hotels such as the Conrad Koh Samui. A free night there would cost 95,000 points or USD$475/night versus THB23,750++ ~ USD$685++ if you paid cash.
The cost can be brought down further if you are an elite member (Silver members are defined as elite members and get the 5th night free with point redemptions as well) with Hilton and stay 5 nights with them, since the fifth night will be free on point redemption. Meaning only 380,000 points or USD$1900 is needed versus the THB131,311.88 ~ USD$3791.
All in all, one should never hoard their points, because hotels can devalue them anytime without notice. I for one have never purchased a single point before, and always feel safer holding on to cash. Buy them only if you really need to stay with them or have a stay coming up.