No.
Well yes, but it depends what you define as "a fortune". Electric mirror housings are about £300 per side and then they need fitting and coding, plus you need a new electric window switch panel. All-in-all you'd see little change from £800.
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Ian
Current: 2021 G21 330i M-Sport
Previous: 2018 A6 Avant S-Line MMI+, 2014 F31 320d M-Sport, 2013 F10 520d M-Sport, 2011 F10 530d M-Sport, 2008 320i M-Sport Coupe, 2002 325i, 2001 318i valvetronic, 1998 318i, 1996 525i, 1990 Porsche 944S2