$100k and $250k are standardized life insurance amounts which over-fund CI by a lot. I can get a $100k 10-year term life at $11/mo and a $250k one for $15/mo. I currently get $100k life insurance through my company so I just did that. Smaller than $100k doesn’t seem worth thinking about.

I do expect to pay out of pocket once I have saved enough money for the cost not to matter, because I want to stop dealing with the logistics of proof of insurance.

I got a $50k whole life policy about 24 years ago, to fund an Alcor neuropreservation. Alcor's prices have gone up since then, but they handle that via charging me an extra yearly fee.

I have $150k in what is termed a universal life insurance plan but it actually looks more like whole life when I look at the terms. I use this to fund neuropreservation with Alcor. For what it's worth, this is 2 times the amount Alcor was charging for neuropreservation at the time I purchased it.

I chose a whole/universal plan since it covers me until death (or technically until I turn 120, at which point it will pay out regardless as I understand it) and I purchased it when I was near the age with the lowest premiums. I think using term life insurance is cheaper but riskier, since you might outlive the term and be too old to purchase additional life insurance at a reasonable rate when you need it, effectively canceling your ability to pay for cryonics unless you have in the intervening time managed to do financially well enough to self-fund.

I didn't self-fund because I couldn't at the time, and even though I expect to later be able to, life insurance offers some legal protections that makes it a nice funding vehicle (I can go bankrupt without risk of losing my life insurance or having it pay out to my creditors rather than the designated beneficiary). Even if you can self fund, unless you pay in advance, you'll want to make sure you use a mechanism that protects the funds and makes sure they go to their intended use.