According to Clark the painting rather shows Johannes Fust (1400 to 1466) an entrepreneur and lawyer from Mainz although when you look through Wikipedia articles about Faust in various languages quite a number including the French Wikipedia still identify the above painting of Joannes Faustus as that of Dr. Johann Georg Faust, the Schwarzkünstler (master of dark arts) who died in Staufen in 1440 or 1441.
It was Johannes Fust who supported his namesake Johannes Gutenberg in his printing efforts by lending money. The result was that in 1455 Gutenberg finally printed 180 copies of his famous 42-line Bible. One year later Fust wanted his 800 gilders back. Since Gutenberg could not pay he had to hand over to Fust his print shop and half of the finished Bibles. When Fust smelled that publishing Bibles was a lucrative business he simply pulled Gutenberg over the barrel. Subsequently in 1462 Fust printed his own bible, the Biblia Sacra Latina, he proudly presents in the above picture.
How did the confusion between Fust and Faust come about? Apparently one of Fust's grandchildren wrote a preface to a reprint of the Biblia Sacra Latina calling his grandfather Johan Fausten. The family liked Faust better than Fust and adopted the name. In addition there was a confusion when people used the label Schwarzkünstler not only for magicians but for printers too.
Was the local saving bank taken for a ride when they bought the picture? Not at all, Jean-Marie Clarke said, Staufen has acquired a painting of another historical person. I would like to add: the Staufeners should make a marketing gag out of their mistake. After all was is not Mephistopheles again who fooled them?