Because Saud Kruger is the ship manufacturer of choice for those with a true feel for elegance which even Gutamaya can't match. The Beluga is the biggest ship in their range, and what kind of a patron would buy an economy yacht? Heck, I'd feel bad if I hauled slaves in my Beluga 'cause you could throw them in the hold, the cells, or the toilet and they'd still be in cushier surroundings than anything a Lakon or Core Dynamics ship could offer, and that's no way to haul slaves around.
EDIT: To everyone saying the Beluga needs a jump range buff, it's like a Jaguar in that respect. If you wanna get there fast choose another ship, the Beluga's all about a comfortable ride.