As I am gearing towards $30,000 of spending on my American Express Starwood Preferred Guest Card, I had the opportunity to purchase gift cards at 20% off and resell at 79% of the face value or 10% off and resell at 89.5%.
The .5% is the difference between buying points at $.01/point and $.005/point. Also note that a .5% is a 100% increase in cost. Because of that, I almost always avoid gift card churning when buying points at $.01/point as it is costly.
The only time I can justify buying points at a penny would be to hit spending goal bonuses. I wound up buying both the 20% off (Barnes and Nobles) and 10% off (Nordstrom) in order to hit the SPG gold status.
I still have about $3,500 left in spending from now to the end of the year. I am still on track to spend $30,000 with the SPG credit card.