Thanks for thinking along. Yes, I think 5000 would be nicer and more in line with the hours spent, though I would also accept less, because I also like what I do. But indeed, I was a bit insulted. Most people don't realize all the work that goes into 'just an image'. And all the hours spent making attributes in the past, the hours of study and experimentation, and the money spent on software and machinery also have to be earned back in due time. And then the taxman says 'thank you' as well. Or actually, he doesn't.
And indeed, it's not really the size, though the amount of detail needed rises with size of course. And I always charge publication rights apart from production of the render (depending on the use), and hope to get some residuals afterwards (from others wanting to use the image).
Sorry I can't show the final in high resolution; it's going to sit in a 180x85cm information panel that slides down into the ground to emphasize older times beneath us, somewhere in Belgium, very nifty.