Drawing after/by Rubens

Arthaz sells on 16 June a "16th century Old Master" drawing of Abraham and Melchidezek, estimated at $2,000 to $3,000.

The drawing is definitely not 16th century though, as it is the same composition as a modello Rubens made for a tapestry. Which raises the question: is it by Rubens, or after Rubens? It's a very good drawing, but it doesn't seem to be a work in progress, a design, and more likely to be a copy after an existing work; the drawing is too certain, too fixed, and too similar to the end result. It still may have originated in the workshop of Rubens, many drawings were made there already, but it may also be a later copy of it. The Rubens can be found in the National Gallery, and the tapestry in a monastery or cloister in Spain. Old copies of the Rubens are known on the art market, so it isn't unlikely that one more copy was made.

For an anonymous though rather good drawing, the price seems too high. If one can attribute it to a specific artist, it may well be more valuable. And of course, if it would be a Rubens after all, the price will skyrocket.