Thanks all for you help em tips, but it is really a lot of work for only $27.50 savings.

When I open this topic, I was expecting to be easy to earn 100 miles (with a survey, for instance), but there is no faster way than buying it... "No pain no gain"

I think I will just wait a few days (until 11-30, last day of "double miles") for the BestWestern points, and then buy the DM.

EDIT: I ended up buy the extra 1000 miles (because there is no signal of the Bestewesten points...)