Ford Falcon: Snapped spark plugs

When I took my dedicated gas Falcon ute in at 100,000 km for its service, which included changing the spark plugs, the mechanic found that they were corroded in the heads. When he attempted to remove them he broke one off in the head, which meant the head had to be removed to get out the part of the plug that was stuck. The bill was $1000, and I wasn't happy. Don't you think Ford should cop the cost; it was their dud design after all?