Congratulations you won the lottery! Now what? (rar)

[The Grim Squeaker]

You could make the castle a lot cheaper to run by partitioning it; only heat the section you actually use, keep the lights off most everywhere, etc.

Though the property taxes would be insane!

Not really, you'd be talking about rural areas, your tax costs to local municipalities would actually be far far lower than the net you'd be paying for, say, a house in central London.

[The Grim Squeaker]

Yeah, but who cares? I´ve got more money than i´ll ever be able to spend. There´s no benefit in increasing the amount of money i have.

If you are a true full-blown hedonist, you'll be able to spend it/lose it easily. You won't have a clue how you did it, but it'll be gone all the same.

Very easily. A prime flat or house is easily tens of millions of dollars in a Class A city, then there's rent and th like, taxes, upkeep, furnishing, etc'. And it might lose over half it's property if oyu invest badly (like, say, most people do).
Want a boat? Go for it, but you might end up spending a few times over what you thought it might, never mind planning, upkeep, crew, docking, fuel, licenses, design, repairs, maintenance (not the same thing), moving it around, etc'.

Same goes for a plane I suppose, even one of the tiny ones. (Which are what, 8-10 million for a new Eclipse ? or 4-5 million? I only know people with ultralight propellor planes from the 50's, which aren't nearly on the same cost magnitude).

People Never think of the upkeep costs.