pay as much as you want for lunch in Vienna

This is definitively no April fools joke: there is a small Restaurant in the Heiligenkreuzerhof directly in the center of Vienna, Austria, called Hollmann Salon, where you can order a three course lunch special and you pay as much as you want.
BTW: just across the corner at Grashofgasse 3 they have a beautiful, small Hotel called Hollmann Beletage with prices starting at 150 Euros for the room. Includes freshly made breakfast, a small garden, real fireplaces and an absolutely cozy atmosphere.