In mid-February, Marriott Bonvoy launched a buy points promotion which was supposed to end this Monday. However, the offer has been further extended to April 13, 2023.
Buy Marriott Bonvoy Points With A 40% Bonus

Through April 13, 2023, the Bonvoy program is offering members who purchase points of more than 2,000 a 40% bonus during checkout. Once again, this promotion expired this Monday however, it is now extended.
Bonvoy members are able to purchase a maximum of 100,000 points per calendar year and the program also lets members share a further 100,000 with other Bonvoy members. So this is an offer to collect a huge sum of points at a reasonable cost.
How Much Do Marriott Bonvoy Points Cost
Generally, Marriott sells 1,000 points for US$12.50 and with this promotion, you are able to purchase the same amount at 0.89 cents each.
In the end, 140,000 points including the 40% bonus will cost US$1,250. This is a great amount as you would need to spend US$14,000 to get the same amount of points. For context, the Bonvoy base member earns 10 points per dollar spent.

Redeeming Bonvoy Points
The Marriott Bonvoy program devaluated and the program is currently using dynamic award pricing. Meaning, the points required to stay change based on time and season. But the rates to redeem by points are typically fixed between 5,000 to around 100,000.
For example, the St. Regis Maldives cost around 84,000 points per night while the cast rate goes up to US$2,000 per night. And not to mention, when redeeming the points, there is a fifth night free as well.
A good example is, during Valentine’s weekend, I stayed at Le Méridien Grand Hotel in Nuremberg where the cash rate spiked to 500 euros. However, the award night only required 31,000 points so this saved me nearly quite a rate.

Summary
Through April 13, 2023, Marriott Bonvoy has extended the buy points promotion where you will receive a 40% bonus on purchased points. This offer will allow you to purchase 140,000 points for US$1250 which I see is worth it. Marriott lets members points sharing so you and another member could purchase points to combine for redemption.
This promotion is not the best I would say as the program offers more than a 50% bonus sometimes. However, it is good for those who need points for their upcoming award stays.