Charge him $200-$400 for a euro mount? A professional taxidermist or skull business charge around $150-$200 for a deer head, and that probably includes a plaque on the upper end price.
Boiling and bleaching cost is not that much. A nice hardwood plaque is not alot of $ either if you go to the right sources.
If I was doing it for my "buddy" I'd do it for free (or a case of beer, or whatever). He'll do you a favor someday. I've done several for friends over the years. If they want it on a nice plaque, I tell them to order one.