I have never really understood why anyone would buy points in a loyalty program, as they are always very, very expensive. But I guess if you needed just a few more points for an award, it might make sense if you want to redeem that reward right away, or if you don't plan on earning points in that program the traditional way for a while.
So for those of you needing a few more SPG points to top-up your Starwood, SPG is currently offering Starpoints at a 20% discount for a limited time.
500 Starpoints is the minimum you can buy, at a cost of $14 USD instead of the usual $17.50, with a maximum of 20,000 for $560. You can theoretically redeem 7000 points at a Category 3 hotel for $196, or 12000 points at a Category 5 hotel for $336. This could possibly be a decent price for points at hotels which are chronically priced high, but likely you will be able to get a better rate just paying cash.
You can also take care of this offer to gift points to someone else, which I guess makes this an OK promotion if you were going to provide the points to someone as an incentive or something of the sort, but I am not sure how useful gifting perhaps 1000 points would be... but then again, that might be why I am not in charge of marketing for a hotel loyalty program.

