in exchange for an extra $300 per year.

I'm inclined to believe this number is a lie, as I refuse to believe you are stupid enough to make mistakes of this order of magnitude.

The claimed $180/year (claimed $300 figure minus membership costs) * 50 or so more years people will live only gives $9k. Safe investment gives you barely enough to keep up with inflation, so you cannot use exponential growth argument.

Real costs are around $100k-$200k reference.

Real life insurance costs increase drastically as you age, and as your chance of death increases. Surely you must know that. If you paid the same amount of money each year, you'd need to pay $2k-$5k depending on your cryonics provider and insurance company overhead.

What will very likely happen is people paying for life insurance, then finding out at age of 70 that their life insurance costs increase so much that they cannot afford it any more, and so they won't see any cryonics even though they paid big money all their lives for it. (Not that chances of cryonics working are significant enough for it to make much difference).