Maybe you can find another one that's cheap, because of a loose barrel or
something, and take the optic out of it to replace yours with......IOW,
"part out" another lens.

That's unfair.  Don't lump all eBay sellers into one category of
"dishonest", as your statement appears to imply, please.

MOST traders are honest, or at least try very hard to be.  Some don't
even know what it is that they are dealing with (having inherited the
item, selling for someone without an account, etc.) and so are not able
to accurately describe stuff, but that's not malicious or intentional.
If you read the WHOLE description, ask a question or two, and check out
the seller's feedback carefully (including looking to see WHY they
might have a negative feeback for something), your chances of getting
exactly what is described are pretty good.  I've bought literally many
hundreds of things off of eBay  [over 900 transactions - admittedly,
not all camera stuff], and I've only been burned once.  Sometimes, if
you are willing to take a risk, you can actually get a pretty good
deal, too.

Example:  I bought a Canon 75-300 IS lens from a description that
stated quite clearly that there appeared to be a hair or something in
the lens, but that it didn't interfere with the pictures (example
pictures were provided).  I took a chance, knowing that a) the
description might be true and it would never be a problem, or b) it
might be a problem but the service charge to resolve it would probably
be minimal if it was what was described.  I got the lens for under $100
including shipping, likely because the truthfulness of the seller had
scared off buyers that didn't believe that it wouldn't affect anything.
I won the lens, it arrived, it did indeed have a hair in it, and, as
stated, it didn't affect the image in any way unless I was completely
stopped down, then it was only a softening of contrast in a very small
area (I doubt that the seller had ever done the micro inspection of the
images like I did).  Nevertheless, I examined the lens closely, and it
appeared as if it might be on the back of the front glass - so, I took
the front glass off (three screws, IIRC), blew it out, replaced the
glass, and solved the problem.

Another non-camera example:  I bought a laminator for $4 - the auction
stated clearly that it was new in box but the feed didn't work [why
they didn't return it is a mystery].  I took a chance, knowing I can
fix almost anything.  I opened it up, and one of the feed roller gears
was missing the screw that held it into place, so it was failing to
mesh up with the matching gear (obviously from the factory that way, as
the cases screws still had their thread-lock on them).  I rummaged
arond in a drawer, found an appropriate screw, and 2 minutes later had
a fully functional laminator which has worked perfectly for almost 4
years now, despite having accidentally left it on for days at a time on
more than one occasion.

NONSENSE!  Are you saying that all eBay sellers are dishonest?  The majority
of responsibility is Paul's since he didn't ask the proper questions prior
to bidding/buying this lens.  It's irresponsible to buy anything without
asking questions.  If you buy something and it is not what is expected you
can only blame yourself for not asking.

As for selling, all my lenses I list are linked to high res pictures, a
proper description, serial number, and a seven-day satisfaction guarantee.
I never had a dissatisfied customer yet.  All questions are answered in my
description, but I am always willing to answer all questions from any
potential bidder.

Rita