Programming a key is a 30 second job (at least in the E39, I'd expect it's very similar in the E53) that takes only a few button presses while sitting inside the car.

I believe it's also referred to as "EWS Pairing".

To the original poster; I would find a cheaper dealer. Keys are generally not something you can do mailorder, as all dealers should ask for proof of ownership and photo ID before letting you order.

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Ben Carufel
IHKAButtons.com
2000 Estoril Blue M Coupe [Garage Queen]
2000 Biarritz Blue 528i Touring [Hauler]
1991 Alpine White 318i Sedan [Daily Driver]
1989 Alpine White S50 325i [Fun Machine]
2002 Chevrolet Silverado 1500HD [Tow Vehicle]