Marriott is currently running a point-buy promotion with up to 40% bonus, at a cost of 0.89c/p. However, bonus levels vary by account, so you need to log in to see your own discount. The discount is fine; I’d recommend it for people with a stay-4-for-1 bonus or those who are just short on points, but not for buying points in bulk to stockpile.
The best tiers are:
- 30% bonus: 2,000–9,000 points
- 35% bonus: 10,000–39,000 points
- 40% bonus: 40,000–100,000 points
I only saw a 35% bonus offer, and the cost screenshot is below (from AwardWallet).