Make with the clicking:
Neal Adams Batman #251 Cover The Joker Original Art (DC, 1973)
So what is this worth?
Heritage has sold "comic art" in the form of Frazetta paintings three times for over $1,000,000 and sold a Herge Tintin black and white illustration (proper comic art ????) for $1,125,000. Those don't help. They have never sold a piece of American comic art for seven figures.
They sold the R. Crumb Fritz the Cat Cover for $717,000, the McFarlane ASM #328 cover for $657,250.00 and the last page of Hulk 180 for the same total. The top Adams lot was the Green Lantern #76 cover, which sold for $442,150.00.
What is this piece worth? That? Twice that? It's original art, so I have no idea! That's part of what makes watching original art so much fun. You can speculate, but at the end of the day these pieces are unique.
I will say I think it's a more iconic image than the Green Lantern #76 cover (although Green Lantern #76 is a more important comic) and Batman/The Joker are deeply ingrained in the wider popular culture in a way that Hal Jordan never will be. There might be a more exciting piece of Adams original art out there, I just don't know what it might be. It will be fun to watch whatever it hammers at.