Not really a "ridiculous" amount of money. It's by invitation only, and you have to spend around $5000 per month on yuor card to be invited. It's not technically the "black" card, it's the Centurion. It just happens to be black.
Some of the perks of Centurion membership:
* Automatic elite status on Continential, Delta, US Airways, and TWA airlines
* Access to Northwest, Continental, and TWA airport clubs
* Elite status at Hyatts, Hiltons, and 6 Continent hotels (Holiday Inns and others)
* Room upgrades at 4 Seasons and Ritz-Carlton properties
* Complimentary international cellphones for any traveling member, pay only for the cost of calls
* Personal shopper and special shopping hours at Saks and Neiman Marcus stores
* Assignment of a personal travel counselor and 24-hour concierge service, who can help you set up parties, arrange travel plans, etc.