Blown head gasket? Need new engine?

Hi everyone, my car started making this noise when starting up. It is a 2014 Toyota Prius Two with 165k miles. My research says it has a blown head gasket, and I’ll need a new engine. Is this right? Does anyone have an idea of how much this will cost? Was this preventable? I would love advice.

I have a video but I can't upload it. It's a quick rattling sound that goes on for 30 seconds and then stops.