I agree some people get carried away talking about how great the pension is. But however you do the math (and it's not straightforward) it clearly does have a lot of value.
The average O5/20 retiree pension is probably worth around $1.2-1.5M, based on what it would cost to buy an inflation indexed single premium immediate annuity with the same monthly benefit. This isn't a perfect comparison, but it's ballpark accurate. It also comes with some flavor of access to Tricare, which is worth something. (Maybe nothing if the USA goes single payer.)
Yes, the payout is taxed at your current marginal rate. The flip side is that during the active duty years, acquiring that pension is comparable to being able to put pre-tax dollars into a defined benefit plan. If you need 8 years to get from the end of your ADSO to retirement, you can consider your income during those 8 years to be augmented by ~$150K/year of pre-tax contributions to that defined benefit / deferred compensation "pension account" ...
This value should probably be discounted a little bit because
1) no sane, young high earner would choose a SPIA as an investment vehicle
2) unlike invested savings, a military pension can't be left to heirs (but the spouse's survivor benefit mitigates that somewhat)
Also, for some specialties, the opportunity cost for delaying entry into a private practice group can be ENORMOUS. This is especially true of surgical specialties where it takes time to establish a practice, build a referral base, grow side income streams related to facilities or other office sales/services. Not so much for specialties like mine, where partnership tracks are a couple years and the referral base is whatever pops up on the hospital's surgery schedule.
Presently the Navy pays me about $275K/year (about $35K of that is untaxed)
I figure the pension in my case is worth about $190K/year based on the # of years between my ADSO and retirement
Add something in the neighborhood of $50-100K/year for moonlighting
So my total income as an AD Navy anesthesiologist (3.5 years away from retirement) is in the neighborhood of $465K/year. Moonlighting easily takes that above $500K. I could do that as a civilian, if I was willing to move where the work was and then work like a dog.
Staying in past my ADSO also got me a FTOS fellowship year. I was paid roughly $200K more that year than I would have, had I gotten out and gone to fellowship as a civilian.
Financially, staying in was easily the better decision for me. Now - after I'm eligible to retire, every minute spent on active duty is a very clear financial loss.
My practice environment is pretty good (coincidentally at the same place
@narcusprince is).