I don't agree with your math, it looks like you would get a little more than $20 for your 10K points.

$331.80 less $311.25 is $20.55.

Works out to about 0.2 cents per point, so I agree it is a horrible use of points.

Unless the rate is so much better than you can do elsewhere.

e.g. if the best deal elsewhere is $500 and you can get $300 through Marriott plus 10K points, then you could say you were getting 2 cpp which would be a good deal

My recent redemptions have been for hotels at about 1.4 cpp. Used to be able to get 2 cpp but not anymore. I won't redeem for less than 1 cpp