i'm in the process of fitting these now.
you can get the innards without caps and mirrors from vag-parts for about 120 each, and you need the revised switch which includes the folding mirror position, and a new controller.
the mirrors also come in 1-piece alu versions for the rs4 which are 300 each..
you then have to run 2 or 3 wires from the mirrors (the extra folding motors) to the controller (which i think lives under the dash at the drivers side) and 1 wire from the extra switch position.
8D2858531G3FZ NSF MIRROR £117.00
8D2858532G3FZ OSF MIRROR £117.00
4A0907440 ECU £ 55.00
4D0959565G01C SWITCH £38.00
these are old audi prices plus vat.
at the moment im trying to get the oem wiring diagrams to find exactly what needs to be connected to what.