Somehow, today, I stumbled (again) over the ancient DOS-function 0x09h. That is the DOS function to print a string. With one amazing quirk: The string is not terminated not by a null character or any of the obvious candidates, but by a ‘$’ sign.
This makes it impossible to use this function to print any string containing a dollar sign. This must be one of the coolest pranks in programming ever, I wonder what the sales people though when they tried to use the function and it would always say ‘The price of the product is ‘!
(I have no idea why it actually is, but this is the best explanation I could think of 
there is probably one person in the world who knew, Gary Kildall (now deceased), but at least I can base this explanation on an anonymous forum post)