It’s always a challenge just to compare salary. Better to compare total compensation.
There is:
Base pay. O-3 pay, as I recall, is nearly double 0-1 at 4 years. That was my favorite pay raise. Military pay may not be subject to income tax in some states, and military members can keep a state of residence their entire AD career, one that works to their advantage, and not be subject to the state they are living in while working there.
Flight pay, sub pay, sea pay, other specialty pays.
Some combat zone pays are exempt from any tax at all.
COLA raise every year.
Longevity raise every 2 years.
All pays are taxable, unless specifically exempted.
Allowances. Not taxable.
There is BAH, Basic Allowance for Housing, based on paygrade, single or with dependents, keyed to zip code cost of living. This can be a good chunk of the tax-free money each month. Meant to off-set housing costs. Use “DFAS BAH rates 2018” to search.
BAS, Basic Allowance for Subsistence, another monthly allowance.
Healthcare. For AD, no premiums, co-pays or deductibles. I didn’t realize the value of this while I was a JO, until I had civilian friends tell me about the money deducted from their salary each month for a healthcare plan. They also had to pay co-pays and absorb deductibles.
Dental care. Ditto above.
Military Pharmacy. No cost.
Military exchanges and commissaries. Tax-free shopping. Often beats local markets, especially in high-cost areas.
Even as a junior officer, I always had plenty of money to pay recurring bills, fully fund IRA and other long-term savings accounts, live comfortably, have a decent car, have an emergency fund, pay all credit cards fully each month, travel and have fun. The Navy paid for both my Master’s while on AD, and the GI Bill paid for additional professional certificates.
Post-separation, veterans’ preference points apply for Fed civil service jobs, and AD time (including SA 4 years) can be used to buy Fed Service time for retirement.
Blended Retirement System (BRS) retirement and Thrift Savings Plan (TSP, military and Federal 401k).
Officers can live very comfortably, and by managing their money prudently, and using their AD time as a platform to launch into higher-salary civilian employment, can become wealthy. Of course, that’s a sliding scale of what feels like wealth.