That's a very good point. It seems there is some dispute about the numbers but the general point is that it would be a lot cheaper to fund SIAI which may save the world than to cryogenically freeze even a small fraction of the world's population.

The point about life insurance is moot. Life insurance companies make a profit so having SIAI as your beneficiary upon death wouldn't even make that much sense. If you just give whatever you'd be paying in life insurance premiums directly to SIAI, you're probably doing much more overall good than paying for a cryonics policy.