The good news is that the discount is not staggered. As long as you buy more than 5,000 points, you get the full 35% off.
At the top end, 30,000 points will cost you $682.50 (£480). Assuming that you convert them to airline miles with the 25% uplift for moving chunks of 20,000 at a time, these can be converted to 37,500 airline miles in the majority of programmes.
This works out at 1.28p per airline mile. This is not a great deal most of the time (you can often pick up Avios for 1.0p) but it might make sense with some other programmes. You cannot buy Lufthansa Miles & More miles directly so being able to get them for 1.28p may well work for some people.
30,000 Starwood points would also convert into 90,000 Marriott Rewards points. If you are working towards a Marriott Travel Package redemption – and they are great value as this article explains – then buying the full 30,000 Starwood points may well make sense.
The rules are straightforward – points post within 24 hours, maximum purchase of 30,000 points per year, your SPG account must be 14 days old to participate. According to the comments below, you will earn 2 points per £1 instead of 1 per £1 if you pay on an SPG Amex credit card.
If you are interested, you can buy SPG points via this link.
(Want to earn more hotel points? Click here to see our complete list of promotions from the major hotel chains or use the ‘Hotel Promos’ link in the menu bar at the top of the page.)