If you thought those wacky European and American graffiti artists who came here in December to transform Israel's separation wall into a massive canvas for "Santa's Ghetto" were a bunch of loons, well you might want to consider that their work transformed those ugly gray slabs into some pretty sought-after concrete.

It turns out, for those who didn't know before, that artwork by Banksy, the mysterious, anonymous, British graffiti artist who spearheads "Santa's Ghetto," is worth a pretty substantial chunk of change.

Keith Spera over at The Times-Picayune in New Orleans reports that Banksy recently turned up in Katrinaville Ground Zero to commemorate the third anniversary of the devastating hurricane.

In a series of pieces you can see on his Web site, Banksy painted a boy riding a life preserver rope swing. He painted National Guard troops looting stereo equipment from a store. He painted a New Orleans brass band with some of them wearing gas masks.

"I looked out the window of my taxi on my drive into New Orleans and remarked: 'There is still so much devastation - I can't believe they haven't cleaned this mess up," Banksy writes on his Web site. "To which the driver stared at me and said: 'This part of the city wasn't affected by the hurricane - it's always looked like this."

Anyway, as Spera points out, Banky's artwork is now sometimes worth more, sometimes much more, than the thing it is painted on.

At a recent "urban art" sale, one of Banksy's pieces - of chimpanzees with sandwich boards taunting humans - sold for $400,000, as in: Creeping up towards half-a-million dollars.

At the same event, a Banksy screen print of Kate Moss sold for $191,000.

"The art-versus-vandalism argument aside," Spera writes, "Banksy's visit was the equivalent of a leprechaun dispensing pots of gold."

Instead of protecting the artwork, though, folks in New Orleans have already obliterated many of Banksy's pieces.

That prompted Spera to make an impassioned plea:

"If clandestine British graffiti artist Banksy ever returns to New Orleans, I'm going to wrap my house in canvas, set his favorite snack on the porch and hope that, like Santa Claus, he shows up in the middle of the night bearing gifts," Spera wrote. "Any little doodle will do."

As in New Orleans, Banksy left his mark on Bethlehem and the West Bank. As in New Orleans, some of the signature pieces - the rat with the slingshot and the soldier checking the ID of the donkey - were painted over.

(There were actually some questions of cultural sensitivity raised about Banksy's artwork, but that's a whole 'nother issue...)

Other Banksy works around Bethlehem, like the girl in the pink dress questioning the soldier, remain.

And other famous artists have pieces on the wall, though some of the artwork is in better shape than others.

So, now that "urban art" is a lucrative business, and now that the wall is becoming a destination spot for said urban artists, considering the fact that there's little solid left to invest in in the United States, maybe it's time to invest in a few gray slabs of concrete...