question Registering first names of people

I see lot of people are registering first names in domain names. My name, names of my children and wife are all taken in .com. .net .org and .xyz. A lot of other first names (and even typos) are registered and showing parked pages. Is there opportunity in registering such available first names? How much people are willing to pay for their names?
I think first names are not a liquid market. The number of big name sales is almost non-existent. Dina is definitely a nice 4 char personal name. How many buyers are there for Dina.com at that price? I did managed to register Dina.biz for $86, regular renewals. Does the tld matter that much when it's a personal domain?
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