Considering snakes if cared for properly are not very likely to have issues compare to other animals you will be better off paying for the cost of treatment in case this happened.
In the last 14 years out of at least 100 adults in my care I have had ZERO issue that means if insurance was $15 per animal per month and I had paid that I would have spend $21000
Now on a side note I wish I had insurance for my dogs especially since one cost me $1200 in surgery every two years but it's a gamble, and I have no issue paying the bill.