In this instance - it is a waste. There are enough wealthy people connected to the Chicago area that raising $3M - if it were such a good cause - would be nothing. Oprah's rainbow-farting unicorn sleeps on $3M every night, with fresh bills laid out for it the next morning.
Between Obama, Oprah, Jordon, all the professional sports teams, and the rest of businesses etc... there is no reason why a city the size of Chicago needs federal money for a science building. It's not a bridge. It's not a highway. It's a planetarium that I have no doubt could have been paid for by the generosity of private citizens.