I have to highly agree with your statement, that 
just becuase someone has a large collection of 
something, that they are not being stingy. It just 
means they were in the right place at the right 
time.  When it comes to Last Unicorn cels, I found 
mine EXACTLY how you are suggesting to this person 
to find them. (not intentionally actually!) I made 
friends with a few cel collectors who happened to 
like the same kinds of anime and cels I liked. In 
most cases actually, I met them due to them liking 
something else OTHER than Last Unicorn, but when 
they heard of one being sold, they let me know. 
I've actually had the opportunity to buy Last 
Unicorn cels twice within the last few months. In 
both cases, I didnt buy all of them, but passed 
the ones I didnt want on to some of my close 
friends who were horribly pining for LU cels, so 
that is a VERy accurate suggestion. When cels are 
this rare, that is just about the only way to get 
them. I'm not saying to kiss ass or anything... 
I'm just so very thankfull that people happened to 
think of me, or were generous to me.... and I'm 
VERY happy that I could help a few other people in 
turn find their dream cel from LU.
so many people love this movie and the cels are 
simply lovely,... its understandable why they are 
rare.