Is attending a more expensive and prestigious foreign university a good financial investment?
Ok, I have answer to this as I did finish all my higher education in the UK, and still living/working here.

Money Buys you a Place But Not a Future: Yes, you can spend money and get to very decent universities; but: 

Exceptions: The Oxford, Cambridge, and Edinburgh are very wealthy and well known and funded, so they don't care much about anyone's money to be honest; however this might differ based on your field. But, the general rule, don't count on getting a place over there by flashing money.

University: Not so many universities currently looking for hire from postdoc level, yet alone PhD level. There is a mayhem over this, just talk to an academic living in the UK. 

Conclusion Back to your question, no by paying extraordinary amount of money you will not get a better financial future compare to finishing your studies within Italy.