Airline pilots at regionals start at about $20,000 a year. 4 years later, they may be making $35,000-40,000. An O-1 out of OCS, OTS, ROTC, Academy, etc... is making $35,000-40,000. 4 years later, as an O-3, you'll be making around $65,000-70,000. I'm pulling in $6,000-7000 a year above normal just in tax free combat pays because I'm deployed so much. I've been tax free 6 out of the last 7 months. Out of about the $60k I've made this year, only $21k was reported to the IRS.
As good as the money is, be forwarned that military pilots are officers who do a lot more than just fly. Officers are supervisors. Officers do more paperwork than you can imagine. Officers sometimes have to take assignments that may not involve flying. Flying is only part of the job. The military gives me $150 a month for "Flight Pay". $1800 a year. This is about 3.5% of my pay. As you can see, flying a 300,000 lb jet isn't worth much to the Air Force. A 1Lt services, finance, or communications officer, for example, is making exactly the same amount of $$ I am, less the $150 flight pay. Of course flight pay goes up to $650 a month at 6+ years flying, but that's basically designed to entice you to sign after your initial 8-10 year commitment is up.