It's because the e Q2 is a tiny piece of software; they've already written this software so the price of putting it into a car as part of the standard map = £0. That's why they don't give you a real Q2!
Also, real Q2 probably does cost a fair bit as it will be under a patent licence, therefore probably only built by third parties who own a patent, and even if Alfa are allowed to build their own they will have to pay a royalty. (Guess who used to do patent law?!)
If Alfa can supply a Q2 diff for £250 and I can't imagine a normal one being massively cheaper, then do they only have to pay royalties if it is fitted to the car? I thought it would be on either a license agreement or a per unit royalty?
Then factor in the cost of the increased chances of a normal diff exploding (like some of the GTA's have), fitted at factory in place of a basic one (also reducing unit cost, due to economies of scale). Really not much in it, but I guess £50 x thousand units = £££
Current Italian Cars:-
2004 Alfa Romeo GT 2.0 JTS
Previous Italian Cars :-
2003 Maserati 4200 Cambiocorsa
2006 Alfa Brera 2.2 SV JTS
1999 Alfa Romeo 156 2.4 JTD
2005 Alfa Romeo 156 2.0 JTS Veloce
2004 Alfa Romeo GT 1.9 JTD
2001 Alfa Romeo GTV 3.0 V6 Lusso
2002 Alfa Romeo 156 2.0 JTS