if this is a grand cru, the wine has a $3-400 shelf price. the wine list price would be around $450-600.
if this is a second or third, and not a grand cru, shelf is a bit over $200, and would be on the wine list at around $300-350.
seems to me that $100 would be a reasonable corkage fee.

for the hundred bucks:
bring the bottle in two days in advance.
keep it on its' side as it has been stored.
to start service, have them put it in a cradle, and open it. never with rotation.
smell the decanter and the glasses for detergent. if detergent smell, rinse twice in red wine. if smell is ok, rinse just once. the rinse wine does not have to be expensive, but should be dry.(i have presumed all along this is a red.) does not take much.
check glasses one last time
have the wine candled with the transfer to the decanter. an 86 probably will not throw much sediment, as it is pretty young.
bring a bottle of something you will really like, that you know will be a good substitute if the 86 is off.
25 yo bordeaux is pretty young, but if it has not been stored properly, or with bad luck, have something decent to keep from ruining the evening. the second bottle should be a corkage free, unless it is on the restaurant menu.