What does waiting really cost me?
Two identical plans, one started later. The money you would have invested is kept aside rather than spent, so what the comparison isolates is time and nothing else.
Your plan
Both plans assume 6% a year, compounded monthly, with contributions paid at each month end. While the start is delayed, the capital and the planned contributions are held at 0%: set aside, not spent, not compounding.
Cost of waiting$26,058Waiting 5 years ends with $355,005 after 25 years, against $381,063 for the same plan started today. That is 6.8% of the outcome, and it goes to a shorter time invested rather than to a worse market: both plans run on the same 6% assumption.
Monthly needed after the delay$557When the delayed plan starts, $40,000 is waiting, held at 0% and not spent. Reaching $381,063 from there takes $57 more each month than the $500 planned, over the 240 months that remain.
The flat stretch is the wait: the money is there, it is simply not invested yet. Both lines run on the same return assumption, so the gap between them measures time invested and nothing else. Contributions are paid at the end of each month.
Show the figures
| Year | Started now | Started later | Gap |
|---|---|---|---|
| 0 | $10,000 | $10,000 | $0 |
| 1 | $16,763 | $16,000 | $763 |
| 2 | $23,932 | $22,000 | $1,932 |
| 3 | $31,532 | $28,000 | $3,532 |
| 4 | $39,587 | $34,000 | $5,587 |
| 5 | $48,125 | $40,000 | $8,125 |
| 6 | $57,176 | $48,563 | $8,613 |
| 7 | $66,770 | $57,640 | $9,129 |
| 8 | $76,939 | $67,262 | $9,677 |
| 9 | $87,719 | $77,461 | $10,258 |
| 10 | $99,145 | $88,272 | $10,873 |
| 11 | $111,257 | $99,731 | $11,526 |
| 12 | $124,096 | $111,879 | $12,217 |
| 13 | $137,705 | $124,755 | $12,950 |
| 14 | $152,130 | $138,403 | $13,727 |
| 15 | $167,422 | $152,871 | $14,551 |
| 16 | $183,630 | $168,206 | $15,424 |
| 17 | $200,811 | $184,462 | $16,349 |
| 18 | $219,023 | $201,693 | $17,330 |
| 19 | $238,328 | $219,958 | $18,370 |
| 20 | $258,791 | $239,318 | $19,472 |
| 21 | $280,481 | $259,841 | $20,641 |
| 22 | $303,474 | $281,594 | $21,879 |
| 23 | $327,845 | $304,653 | $23,192 |
| 24 | $353,679 | $329,096 | $24,583 |
| 25 | $381,063 | $355,005 | $26,058 |