There are a few locksmiths that can come up with a duplicate. When I checked in my locale, the price was even higher. I suspect they are simply buying from the factory and adding 10%. So yes, the dealer is pretty much the only source. IMHO, that's good, reduces theft risk.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970