So, I take my '01 Blazer (4.3 L, automatic, air) to my local mechanic
(who I do trust, incidentally) to get an estimate on some work... part
of which would be changing out the 6 spark plugs. Now, I'm thinking
that the parts for this particular job... 6 OEM AC's are gonna run me
about $2 each. Imagine my surprize when I'm told that they will run
more closer to $12 each!! Both my mechanic and the parts house he's
getting them from recommend this plug for this application. Now, I've
heard of Mercedes-Benz' that require a $12 plug... but a lowly Chevy
4.3 litre? What's you guys' opinion? Am I getting hosed?

Thanks!

They list for $16.90 each.

You're getting a deal.

Why are they so expensive?

Define expensive.

More then $3 a piece.

To answer your original question; because they're not
one size fits all might maybe sort of work replacement parts.

Yes. $1.79 and up at AutoZone. $1.46 and up at Rock Auto.

So what's different about that 4.3 that requires it to use these $13
plugs when my 1989 4.3 gets by with the $3 ones?

Different ignition system
Different fuel system
Different cylinder heads
Different camshaft
Different emissions system
Different emissions requirements
Different emissions monitoring

Don't take my word for it, go ahead and try installing the distributor
cap from your 89 on a 2001.

Why even spend that much, a 14mm bolt is 78 cents at Fastenal.