That 9% difference that you quoted is deceptive because it's largely based on housing costs. And the idea that a typical 3BR/2BA house in Iowa City is $389K in Iowa City but only $371K in Baltimore is silly for at least a couple of reasons. First, if you work in Iowa City you don't have to live right in Iowa City. It's easy to find a nice 3BR/2BA house in a surrounding community in the $250-300K range and still be within a 15 minute drive to work. And the only reason the median house in Baltimore is only $371K is because that figure includes houses in neighborhoods that even Club215 admits he would never venture without a specific reason, let alone live there. Sure, you could probably buy a 3BR house in Sandtown for $150K, so long as you don't mind feeling like you're living in an episode of The Wire. But if you want to live in a neighborhood that's anywhere near as safe as most parts of Johnson County, Iowa, then you can expect to pay more like $400K.
22% of that additional $25K in salary goes directly to federal income taxes. 7.65% goes to FICA. 5% goes to the state of Maryland. 3.2% goes to the city of Baltimore. 38%, or about $9500, is gone before it even reaches your bank account.
Rent is about 59% higher in Baltimore than in Iowa City. So if you're a recent college graduate who can't afford to buy a home yet, you're going to be paying an additional $8500 a year in rent. Now $18K of your pay raise is already gone. And that's before you pay higher prices for trivial things like groceries and utilities.
Wanna own a car? Prepare for sticker shock because auto insurance rates in Baltimore are roughly twice as much as they are in Iowa City. If you're married and your wife absolutely insists on also having a car of her own then you're barely going to be left with enough extra cash to buy some Orioles tickets.