I know you're just using this as an example, but it begs a question I've struggled with: is there any actual proof that marginal tax rates reduce productivity in high earners?
On its face it makes perfect micro-economic sense, but that's like saying a cache will never miss or a cow is perfectly spherical. It just doesn't match up with real life experience. I've never once heard someone say "well, I'd ask for that raise, but they're going to take so much in taxes it's just not worth the effort".
Anecdotally it hasn't changed my motivations one lick as I've moved up tax brackets, to the point that I recently joked with my dad "I guess I'm done trying now!" when I stopped qualifying for a certain tax credit after I'd negotiated hard for a nice raise.
Not-so-anecdotally there's plenty of research that has shown that money (in and of itself) is a terrible motivating factor[0].