So assuming this is a "WTF could you spend that much money on?!?!" question, and avoiding obvious things like big new houses/saving tons/giving away a bunch and such, I can say, with confidence, that I could find a way to spend almost any amount of income.
First, I'd "buy" a whole mess of help around the house -- full-time gardeners, housekeeper, chef. That's a couple hundred grand a year. And of course the lawyer and accountant fees to make sure it's all done legally and taxes are paid, etc. Oh, and a personal assistant to manage all logistics for me. And more private training sessions at my gym. Dietician, concierge medicine, etc. I could easily spend $500K/yr making my daily life easier and healthier.
Then I'd increase my travel standards. Depending on how much money I'd need to spend, I'd fly business every time or upgrade to private, hire a car to drive me around, maybe use a helicopter to do things conveniently. I would take many, many more weekends up in NYC and stay in nicer places, get really excellent seats to shows and events, so that's easily like $5K/pop without even trying.
I would also very happily and easily get season tickets to my favorite hockey and NFL teams -- maybe a suite! And we haven't even talked about hobbies -- hell, I'd have to build a workshop just to store all the stained glass I'd buy, and boy it would be lovely to cook with some white Alba truffles in season, you know? And DH's hobbies aren't cheap: woodworking, all sorts of techie stuff, mountain biking, skiing, scuba diving -- you name it, if it involves expensive gear, he's into it.
All of these things allow fun with little of my own time/effort, along with plenty of privacy. I could look out at a beautiful yard without having to spend hours and hours myself. I could pop over to a game without having to schlep through the big long public entrance lines or wait in the interminable pile of cars trying to leave after. And I wouldn't ever have to spend my own time on planning all that shit, which is my total kryptonite and causes a ridiculous amount of mental stress.
Really, I'd have to get to hedge fund levels before I'd struggle with how to spend all that money. And then I'd just start buying more homes anyway, maybe a plane . . . .
Of course, if I really did make, say, $10M/year and was living paycheck to paycheck, the first thing I'd do is put like 95% of it into savings, because spending that amount of money without a safety net would make me throw up. But my larger point is that there is always a higher level of something out there; we just have no insight into anything beyond the folks who are maybe two steps up the ladder from us, so we can't conceive of how folks further up spend all that money and assume that if we had that same money, we'd spend completely differently and not be nearly as stupid. But the human capacity for greed, sloth, and immediate gratification cannot be overestimated. If someone has extra money floating around, someone else is going to figure out a way to get it, no matter the amount. And if someone has created something that only the richest can have, someone is going to spend the money to get it, regardless of how stupid and unnecessary it is.
FWIW, I know this because we now make something like 15-20x what I made 40 years ago. And I very clearly remember back then thinking about how, well, 2-3x my salary would be fantastic and allow me to have everything I wanted. And I can still think of other stuff I would be more than happy to get if I made 2-3x our current salary.
This is why I'm here, btw. Not because it comes naturally to me not to want stuff. But because I am really, really good at coming up with more ideas for cool stuff I do want.* I need to remind myself regularly that I have a ridiculous amount of luxury already and adding metric shit-tons more wouldn't actually make me happier -- and that the world isn't one giant Powerball jackpot and doing the things I'd need to to get all that extra stuff would "cost" me far more than it would ever be worth.
*You know what the #1 thing on my Powerball list is? You give me $100M, I am sending someone around to all the flea markets to buy up all of the cutesy Hummel-type figurines, and then I am going skeet shooting with them. I figure it's a service to humanity. Like I said, I am very, very good at coming up with creative ways to spend money.