Is a crown chipping in 2 days something usual?

I needed a crown for my front tooth. They had issues matching up the color so I actually went to the lab. In total there were 6 different attempts to match up the color before they got it right. The crown was in for two days and then chipped on the side. I went to the dentist today and he said it was due to my grinding and not wearing my bite guard so I would have to pay 50% for the replacement ($500) for the replacement. Does this seem right? Even with grinding - should it have broken in two days.