You are very right!
> 
> My logic is this.  If it is difficult or impossible to trade or sell 
> greenhouse or in vitro propagated specimens of a rare plant, THEN those 
> who desperately want them will collect them.
That is exactly the point. Plants that are rare (meaning rare on the 
market, not necessarily in the wild) yield a higher price. 
They are kept  artificially rare by CITES, ergo they are in 
demand and people go hunt for them. A very good example are the 
Paphiopedilums. Since the infamous CITES raids over here in Germany, 
prices habe gone up by 500 to 2000%. So the profit is higher although 
(possibly) less plants are being sold.
> If a plant is rare in the wild, 
Already Hooker (sub. Bot. Mag. t. 7102) indicated that one should be 
careful with the designation of a plant as 'rare'. This term is very 
often used by certain CITES people to make propaganda for CITES. I 
have already said before, that very few plants in the wild are really 
rare (unless their habitat is destroyed). Some are rarely found, but that
is another story.
> I imagine if a poacher went in and collected samples of an endangered CP 
> it would probably do a heck of a lot less damage than the acres of that 
> species that would probably be wiped out that same year by farming, 
> mining, housing developments, etc. 
You are absolutely right.
Ronald:
> Exactly how do CITES people declare habitats extinct?  I have never heard of
> such a thing in over ten years of dealings with CITES.
In that case, I am afraid you are not reading too much of the 
literature and not listening too much to talks by CITES propagators. 
What arguments do you think they used to put all the slipper orchids 
on Appendix 1 ??? And to go back to Pitcher plants, some of them 
literally cover mountain slopes!
Happy CPing
Guido