No amount of evidence will convince someone who has "faith."

The fact that many "crop circles are alien" proponents are making money off the phenomenon is indeed one factor, but a more important one is their need to defend a position that they have staked their entire reputation on. Few people are willing to admit that much of their lives has been devoted to something totally wrong, and barring some "road to Damascus" change of mind*, you are rarely successful in getting them to see the truth no matter what evidence you supply. Does anyone doubt that if the "Face" on Mars currently had dozens of spacesuited geologists crawling over it, nailing down for all time that it was a natural phenomenon, that people like Hoagland would not STILL be making bizarre excuses for it being an artifact?

Heck, try arguing with a socialist some time.

*An interesting phenomenon. Some enthusiastic supporters of a given position undergo a complete switch of perspective, often going as far in the other direction as possible. Very few end up as moderates--kind of like the Earth switching poles. There are a number of examples of this in politics, like David Horowitz.