A new tumbler and key will be more than $20.
I bought a timbler and 2 key for the 80 240D, and it was $90 for the tumbler and $15.84 for the second key plus tax.
There might be a variable in price differences between dealers, I don`t know.
You won`t get the key or tumbler the day you order it. It is over nighted from Texas where they keep the secret codes

.
I had to replace the lock assembly`s on the 80 240D and 85 300D. I had a good used one for the 80, but had to order a new one for the 85, it was $172.00. but after 25yrs and 30yrs, they do wear out.
Charlie