You can get them (front discs) from Ferrari/Maserati at the £500 a pair price (plus fitting!) for what I would consider to be fairly ordinary one piece discs which should be about £150 a pair.
Brembo who used to make aftermarket versions are sold out and are not restocking.
These discs in various drilled configurations are the same for Ferrari 550 Maranello, Ferrari 456, Maserati 3200GT, and Maserati 4200. So owners of these cars are in in the same boat.
It is a bit of a rip off and doesn't do the Ferrari/Maserati brand any favours, but I guess they can do this as part of their "If you can't afford a Maserati/Ferrari you shouldn't have one" concept/policy and to ensure that they continue to make profit from owners of used cars.
This of course means that whilst ownership is very exclusive and exclusive can mean desirable, they will not be able to compete with BMW or Mercedes in the big exec market as those cars are bought by pragmatic accountants.