The OP's car I was using as an example wasn't a $15-20k car in my market (I sold my perfect '01S for less 2 years ago). And acceptance of risk in buying a 14 year old used car is a fact of life. Do I wish Porsche made a perfect engine? Yep. Does it hurt if it happens to your car? Sure does. Happen to everyone? Not even close. Every year more crash than engines blow. (Wait till you see the body shop estimate for fixing what on a Honda would be $2.5k. Makes a Raby big block look almost cheap.)
But have the issues been known for many years? Yes. Fixes available for most of the serious ones available for years? Yes. So due diligence and preventative maintenance could have reduced the probability. But when you don't...then you are accepting risk. (I did and got away with it but I also documented and posted all the known problem areas I was aware of at the time and it is
web available so I wasn't fooling myself. I also bought at a price point where I could afford the worst.)
Raby rebuilt engines aren't the only ones out there and lots replacement engines go for less than you are citing. I've seen people buying engines from wrecks for half the price of their car's running condition value.