This isn't all Bush, as Obama made the decision to continue the war in Afghanistan. But Bush set in motion policies that wound up costing about $4 trillion.
It's also cost a lot of lives. The most accurate data we have are on U.S. military casualties: 6,648 service members have
died in Iraq and Afghanistan to date, a large majority of the deaths occurring under Bush's presidency. Civilian casualties are harder to count. The UN mission in Afghanistan
estimates that 14,728 civilians died there between 2007 and 2012. That, of course, does not include casualties of the invasion and occupation between 2001 and 2006.
Iraq is even harder to track. Iraq Body Count, an NGO devoted to tallying deaths in that war,
puts the number at between 112,114 and 122,644. The real number could be much higher. The World Health Organization
published a study in the
New England Journal of Medicine putting the death toll between 2003 and 2006 at 151,000. The medical journal
Lancet published a
study in 2006
estimating that around 655,000 had died. That survey in particular was very controversial, but regardless of whether upwards of 600,000, or "only" over 100,000, have died, the war has killed a whole lot of people.
George W. Bush’s presidency, in 24 charts
Very costly any way you measure it.