Having a special message on my government issued plate isn't too high on my priority list so I imagine that even if I were a billionaire I wouldn't spend more than $500 USD on a personalized plate. Can't say for sure since I've never been a billionaire though. Many things could change!

The most memorable vanity plate I've seen was on a late model Corvette circa 2010 that read either PAIDCASH or PDCASH.