For the record, the Marriott elite bonuses are:

Silver - 20%
Gold - 25%
Platinum = 30%

Doesn't change your analysis much.

Also, there is a Marriott promo starting March 1 which can yield up to 30,000 points, and one can get a room at a Marriott property for as little as 7,500 points.

Finally, the cost (in points) per night for an award decreases the more nights you get, up to a maximum of seven nights. For a top-level property, this amounts to about 18 to 21K+ points/night.

Take that, Holiday Inn!