That only matters if it happens literally at the same time as a failure of your primary storage. If they increase the price you can just close your account and move the backup to another service.
The probability of a hard drive failure or ransomware at the same time as backblaze or aws going out of business is pretty much not worth thinking about.
The probability of an attacker using the api key in your backup script to destroy the backups is far more possible.
That only matters if it happens literally at the same time as a failure of your primary storage. If they increase the price you can just close your account and move the backup to another service.
The probability of a hard drive failure or ransomware at the same time as backblaze or aws going out of business is pretty much not worth thinking about.
The probability of an attacker using the api key in your backup script to destroy the backups is far more possible.