"When bitcoin hits a million dollars it's not gonna matter whether you bought in at 60k or 20k." This is a fallacy.

The reality is that your investment at 20k results in three times as much bitcoin. This could be the difference between a $100k return vs a $300k return (or 1 million vs 3 million).

The point, given that short term price is unpredictable, is to always have some cash available to take advantage of significant moves to the downside. These investments go the furthest.