What does it cost?

I refuse to keep track of what I put in to my cars. It takes the fun out of it.
Yup!

Life's too short. If your missing mortgage payments - that's one thing.

But I've never heard someone in the last days of their time say "damn I'm glad I saved that extra few K and didn't take that trip/buy that car/ etc"

It's a hobby. For fun. There are certain cars that may (may) return an investment on a rebuild. But don't plan on it. Build it. Drive it. Enjoy it.