Hi
You right the window rubbers are expensive. Wasn't always the case though.
Superformance used to do the front screen rubber for £118 plus the vat and the rear screen for £80 plus the dreaded. I got a complete set of quarterlite rubbers for both sides for a mere £117.00 inc packaging/ delivery and vat! I only wished I'd have gotten my front and rear rubbers at the same time
There is alternative though. You can use a standard rubber that comes on a roll
as jhc and deon used but to be honest it looks crap. Have you tried re-originals an america company (I think) who do alot of replacement rubbers and seals for ferrari's?
Ian