A sharp exchange over U.S. money for Ukraine turns into a broader attack on the idea that governments should spend taxpayer money on causes their advocates won't personally fund.

• Mark Cuban says the U.S. should help Ukraine but admits he has no worked-out position on it.
• Pressed on it, he confirms he has personally given nothing, despite his own Ukrainian family roots.
• His answer is that his focus is fixing American healthcare instead.
• The pushback: forcing other people to pay is not charity, and those calling for aid never volunteer to go first.

Outlook: Expect this "you first" line of attack to keep showing up as Ukraine funding stays a live political fight in Washington.