You can figure about $3,333 per month of passive income for every one $1 million in value (that is assuming a 4% per annum withdrawal rate), so personally, I believe that $2 million would be decently comfortable enough for a passive income of $6,666 per month.

Of course, individual standards, lifestyle choices and even past standards (which affect expectations) are going to vary, and more dollars can be better in terms of being able to enjoy more comfortable aspects of life and having more flexibility.....and even cushion.  I personally would NOT consider $1million to be a starting point, unless you were to believe that $1million were the likely bottom of a cycle.. so maybe right now, we could consider $3,000 per BTC would be the bottom of this cycle, so in that regard, we would need to have a minimum of 333.33BTC ($1million/$3,000) portfolio to sustain a $1million value and to be able to passively (and sustainably) cash out at $3,333 per month.

We could end up speculating wrong about the bottom of wherever we are, so lets say that someone wanting to retire speculates that $10k is going to be the bottom in the future, and s/he speculates that s/he needs $2.5 million sustainable to be comfortable pulling the retirement (fuck you) lever.  that is 250 coins, and yeah if we go up to $100k and the person diversifies out of bitcoin, then that is another story too, but it does seem good to be realistic in terms of thinking about the bottoms of markets rather than the tops, even though there could be some decent diversification practices that are employed at the tops in order to feel better prepared for the extremes of the potential bottoms.