After market keys are brass, and as they wear down the brass can cause problems in the tumbler expecially if wd-40 etc... is sprayed to lube things. It tends to gum up things.
The Dealer keys are made of steel, and are about $17 ea.
Using the ignition tumbler off the internet is ok as long as you don`t loose your keys. Do you know the Vin# the tumbler came out of? and if you did, you would be SOL trying to use a different VIN than your own for your car.
I just bought a new tumbler and a second key for the 240 from the dealer.
timbler lists for $100, and he out of the kindness of his heart.let me have it for $90. the key list $17.50 for me $15.84. total with $6.50 shipping/tax = 121.07.

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$40 sounds real good.
Charlie