My point is at age 22...I don't know a single person who has 100K to invest. Therefore there was no opportunity to invest this amount.
However, I understand what you are saying...I am just saying you are grossly overestimating it.
Assuming you were investing over a 10 years period post residency instead of paying off loans. And then contributed nothing to it until you were 60 years old you would have $394,329.20 (assume 5% interest rate....this is interest growth after taxes removed)
$394,329.20-100,000 = $294,329 "opportunity cost".... is not 750,000 as you said though. *I put it in quotes because you never really had the opportunity to invest if you did not have the means to make the cash in the first place.
I agree few 22 year olds have 100k lying around to invest. I didn't mean to imply that.
So I did a crude crunching of the numbers and came out drastically different than you.
For the student who takes out 100k in loans
With 100k Loan Total Debt Interest Rate = 6.8%
Age 22 MS-1 (25k/yr) 25,000 Assume 8500 sub, 16500 unsub
Age 23 MS-2 51122 Assume 17000 sub, 34122 unsub
Age 24 MS-3 78442 Assume 25500 sub, 52942 unsub
Age 25 MS-4 107042 Assume 34000 sub, 73042 unsub
Age 26 Residency 114321 Assuming just deference
Age 27 Residency 122095 Assuming just deference
Age 28 Residency 130397 Assuming just deference
Age 29 Residency 139264 Assuming just deference
Age 30 Payment Yr 1 129089 Monthly Payment @ 1533 1532.87
Age 31 Payment Yr 2 118222 Yearly Payment @ 18394 18394.44
Age 32 Payment Yr 3 106615 Interest Compounded once at end of year
Age 33 Payment Yr 4 94220
Age 34 Payment Yr 5 80982
Age 35 Payment Yr 6 66843
Age 36 Payment Yr 7 51743
Age 37 Payment Yr 8 35617
Age 38 Payment Yr 9 18393
Age 39 Payment Yr 10 -1 Total Paid 183944.4
Thus the total cost of the loan on a standard 10 yr repayment plan without IBR and standard deferment during a 4 year residency is ~184k. Assumes student took out 25k/year.
If a person without the 100k debt invests the same amount as the payments at your stated 5% ROI during those same 10 years, that amount grows to ~645k by age 60.
For student w/o 100k loan who invests an equivalent amount
W/O 100k Loan Total Gain
Age 22 MS-1 (0K/yr) 0
Age 23 MS-2 0
Age 24 MS-3 0
Age 25 MS-4 0
Age 26 Residency 0
Age 27 Residency 0
Age 28 Residency 0
Age 29 Residency 0 Interest Compounded once at end of year
Age 30 Payment Yr 1 18394 Input 18394 per year, ROI = 5%
Age 31 Payment Yr 2 37709 Input 18394 per year, ROI = 5%
Age 32 Payment Yr 3 57988 Input 18394 per year, ROI = 5%
Age 33 Payment Yr 4 79282 Input 18394 per year, ROI = 5%
Age 34 Payment Yr 5 101641 Input 18394 per year, ROI = 5%
Age 35 Payment Yr 6 125117 Input 18394 per year, ROI = 5%
Age 36 Payment Yr 7 149768 Input 18394 per year, ROI = 5%
Age 37 Payment Yr 8 175651 Input 18394 per year, ROI = 5%
Age 38 Payment Yr 9 202827 Input 18394 per year, ROI = 5%
Age 39 Payment Yr 10 231363 Input 18394 per year, ROI = 5%
Age 40 Interest Only Yr 242931 Input 0 per year, ROI = 5%
Age 41 Interest Only Yr 255078 Input 0 per year, ROI = 5%
Age 42 Interest Only Yr 267832 Input 0 per year, ROI = 5%
Age 43 Interest Only Yr 281224 Input 0 per year, ROI = 5%
Age 44 Interest Only Yr 295285 Input 0 per year, ROI = 5%
Age 45 Interest Only Yr 310049 Input 0 per year, ROI = 5%
Age 46 Interest Only Yr 325551 Input 0 per year, ROI = 5%
Age 47 Interest Only Yr 341829 Input 0 per year, ROI = 5%
Age 48 Interest Only Yr 358920 Input 0 per year, ROI = 5%
Age 49 Interest Only Yr 376866 Input 0 per year, ROI = 5%
Age 50 Interest Only Yr 395710 Input 0 per year, ROI = 5%
Age 51 Interest Only Yr 415495 Input 0 per year, ROI = 5%
Age 52 Interest Only Yr 436270 Input 0 per year, ROI = 5%
Age 53 Interest Only Yr 458083 Input 0 per year, ROI = 5%
Age 54 Interest Only Yr 480988 Input 0 per year, ROI = 5%
Age 55 Interest Only Yr 505037 Input 0 per year, ROI = 5%
Age 56 Interest Only Yr 530289 Input 0 per year, ROI = 5%
Age 57 Interest Only Yr 556803 Input 0 per year, ROI = 5%
Age 58 Interest Only Yr 584644 Input 0 per year, ROI = 5%
Age 59 Interest Only Yr 613876 Input 0 per year, ROI = 5%
Age 60 Interest Only Yr 644569 Input 0 per year, ROI = 5%
Feel free to suggest tweaks in the model.