In addition to Curtain Rod's comment... Having read pages and pages of comments from guys leaving the military... Most of the reasons have little to do with money.
Most have quoted bad leadership with no loyalty from their bosses, just ****ty managers looking for their next promotion. Poor career management. Decreasing conditions with poor work life balance. And finally the organization itself is poorly managed by numpties who waste money on stupidity whilst telling you to be more efficient. All Sound familiar?
To quote one of the comments I read... "You've taken the best job in the world and made it suck." Sound familiar?