Monaco real estate is currently going for about 3–4 times what comparable properties cost in Newport Beach, CA. If anyone's interested, feel free to PM me—I'm in the process of obtaining residency here in Monaco, and there are quite a few hurdles to navigate.
It's particularly expensive for Americans. You need a local bank account, plus either a lease of at least 12 months or property ownership. I managed to lease an apartment for roughly 1.4% of its current market value (including all add-on fees).
Banks typically require at least 5 million in deposits to work with U.S. citizens. They often want that money to sit untouched in their accounts for 6–9 months (earning zero interest) while you complete the residency process, plus they charge a 40-basis-point custodial fee—and additional fees on top of that. It's quite an adventure.
Tax advantages? They exist, but they're situational—especially useful if your circumstances are unique or if you're a former CPA (like me) who enjoys a challenge. There's particular value in reducing estate taxes. It's ironic: many of us on this board started buying BRK 30 years ago, worried about Warren Buffett passing away before we had enough money. Now that we do have money, we're worried about us passing away and the estate tax hit.
Jim and Manlobbi know far more about Monaco than I do, but being American adds its own unique quirks and complications.