Ugh... no. If you want to be financially independent and make bank, you better learn to invest and make money work for you in order to take advantage of that 15% loan term capital gain tax deal. Once you pass the 300K line, you will only keep 50% of every dollar earned. Not worth it especially if it's taking 60-70 hrs of your week to crank that much money. Let's put some perspective to either methods:
1) You're an ortho bro making 600-800 K/yr while paying 50% total tax for all income over 300K
2) You're insert specialty bro making 250-300 K/yr while having investment money earning you can extra 200K a year at the tax rate of 15%
In term of money, both will come out equivalent with the 2nd scenario happening at a 40 hrs/wk workload.
uhh what? First, what are you investing in that pulls 100% of your salary every year? If you're making 200k/yr after tax I highly doubt you're going to pull 200k/yr in capital gains, that's a 100% return (if you ignore all your other expenses) and even the best funds don't hit that rate (not even close). Second, the person making 600-800k/yr isn't going to not invest their money either so your example where the random specialty person is pulling extra income and the ortho guy is not is comparing apples to oranges.
edit: Ok, time for some math. Both of these people live in a state w/ 0 state income tax, like Florida to simplify it a bit. I'm also assuming your numbers are correct. I'm also aware that doctors don't really earn hourly wages, I just included that to make the numbers more comparable
I'll take the worst conditions you gave for the ortho: 600k/yr at 70 hrs/week x 52 weeks/yr
Post tax (according to the calculator because I cba to calculate the brackets right now)- 394k/yr or $108/hr (fwiw, it goes to 126/wk at 60 hrs/wk)
Other guy: 300k/yr at 40 hrs/week
Post tax (same calc, same conditions)- 208k or $100/hr
Ignoring capital gains, is working 30 extra hours a week for +$8/hr worth it? That's up for debate. But that's also the worst set of conditions you gave
With capital gains, the other doc needs to make 186k/yr in investments (ignoring lt cap gains tax) to match the ortho doc salary if they don't invest a penny. That's already impossible unless there's something that gives you 89% per year of your entire income in growth. Even if you get 100k/yr in dividends and external income (somehow), your portfolio has to grow >40% per year to match the ortho
If you can put together a portfolio that consistently grows by 40% per year might as well quit your job as a doctor and open a hedge/mutual fund.
By the way, the ortho is taxed 20% on investments whereas the other doc is taxed 15%. If the two both invested, your portfolio would have to increase by >$3.7 MILLION/yr before you matched the total gains+salary of the ortho
So if you want to go into a non-competitive specialty and invest to match the salary of the highest paid specialties, it's not going to happen
If you think your QOL will be better because you're working 30 hrs/week less and only earning $8/hr less than the most competitive specialty (based on your worst conditions) then yes there's no reason to go into a competitive specialty
edit2: I bumped the # of hours for the other doc to match the ortho and they still have to make ~9%/yr on cap gains to match the ortho salary assuming the ortho doesn't invest a penny. Although I'm starting to think 600k on 70hrs/wk heavily lowballs what an ortho makes (or 300k on 40 hrs/week is really generous) because if this is the case the specialty you go into really wouldn't matter
edit3: I know that no one really looks at their portfolio in the short run like I did and that analysis ignores cmpding interest. So more realistically, the ortho in a 30 yr career is going to make like 12m. The other doc is going to make 6m in the same time span. If you invest half of your income over your lifetime (3m), you'd need like 2.4% interest (fwiw this is way oversimplified and based on the rule of 72 but you get the idea, I'm drunk and tired rn) which is definitely attainable (apple bonds were considered "risk free" and iirc gave 3% returns). But that assumes the other doc isn't investing which is absurd. If he invested 1/2 his salary, he'd get an extra ~6m
edit4: ok sobering up and can't fall asleep still so let me organize all that **** I wrote
1.) The first thing I wrote up is for how much you need to make on investments of 1 year of salary to match the 1 year salary of one of the highest paying specialties in one year, in response to what you wrote in your post about the 200k/yr return in investment. If you invested your entire salary of 200k, you would need to make 86% return on that investment (ignore lt cap gain tax) if in the following year you wanted a take home income equivalent of an ortho
2.) The second thing I wrote is more realistic and accounts for compound growth. You would need to make 2.4% (more like 4-5% because you need to pay a fee for the guy managing the portfolio) return per year if you wanted the life time earnings of an ortho assuming the ortho does not invest.
So there are diminishing returns for the higher end specialties but assuming you do the same thing with your money as an ortho vs another specialty, you will never match the total earnings as you would in ortho or any other higher paying specialty. The extent to which the diminishing returns matter is up to you