Thermite is actually a pretty good one--death is a lot more like erasing a drive using thermite than erasing it by overwriting it with 0s and 1s.

Just dying isn't much like erasing a drive with thermite. Damage from ischemia takes time. It's not like your brain instantly turns into pudding the minute the nearest doctor says "time of death". Now, dying and then rotting in the ground somewhere for 50 years is a lot more like erasing a drive using thermite than overwriting it. That's the point of cryonics.

Edit RE insurance:

Insurance is a way to avoid catastrophic losses. It is not a way to reduce costs. On the average, an insurance company's customer will pay more in premiums than the amount paid out by the policy. If $X is too much money, $X is too much money even if paid by insurance.

Of course this is all true. However in the case of life insurance it is also a way to offload the expense to your future self, who presumably has more income than you. If I had to pay the whole thing upfront it would be certainly impossible for me to get cryonics at my current age.

Actually, now that I think about it, it is potentially not true that you would pay more in premiums than the payout, since insurance companies can make a profit on people who let their insurance lapse before dying (which is apparently quite frequent in life insurance). Picking two random life insurance company's websites, it looks like a healthy human of my age could pay as little as 75% of the payout in premiums, assuming a life expectancy of 70 years.