As for the card, I don't think that's obscene. If they can afford to get that card, and it makes them happy, more power to them. I know if I were rich, I'd lead a pretty modest lifestyle. But baseball cards would be my weakness.
I agree they're probably doing so for registry reasons. Or, maybe the buyer is a Molitor super collector, and he wants that one crown jewel for his collection. Hell, if I could afford a 1975 Topps Robin Yount PSA 10, I'd click "buy it now" so fast I might ruin my keyboard. 
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Building these sets: T206, 1953 Bowman Color, 1975 Topps.
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