Sounds typical. If you are local you can also try walking in with the part to bacons. It always amazes me what they have. Or check the chain plate itself to see if there are any markings and try to go back to the supplier. It wouldn’t surprise me that this will end up being a stock part available from another source for a fraction of what beneteau charges.
I had a bleed valve go bad on my westerbeke. Westerbeke wanted $30 for the part plus $15 for shipping/tax, and I would have to wait 2 weeks for the part. I typed the part number stamped on the part in a google search and found it listed as a Chevy radiator valve stocked at my local autozone for $6. 100% the identical part from the same manufacturer. She was on the engine an hour later. Sometimes you have hustle a little.