Well, prices have gone up, particularly on things from Europe. Centerline sells an aftermarket head gasket for approx. $30, but a real Alfa one through Jon Norman, etc., is going to be more.
Plus shops have to include a mark-up to stay in business. I don't know if $99 is extortionate or not, but I wouldn't automatically assume so. Plus, remember that the cost of parts is usually a relatively small percentage of the total cost of somethign complicated like a head gasket/valve job, all of which could set you back on the order of $1200 if valve grinding is needed.
If you're not happy with Barber's, check with Steve Bonney, who left there to set up shop on his own in Sac. In my experience, he's good.