Race blocks

I see the aluminum low deck on Indy's web site. I don't know the price and don't want to load a PDF deal into my phone to see the price. I'm going to assume it's around 5-6 grand. That's too expensive for me. I'm leaning more towards the 400 block I have. Moper, you are very knowledgable on this subject. What actually goes wrong with these block when they're pushed hard? I see you don't believe in girdles. Does the block crack and grenade or start spinning bearings, or what?