I've had individuals post offers on cels in my 
gallery. Some of these have been low ball and 
some of them ridiculously low-ball.... (in my 
opinion anyway). I have resisted the urge to rant 
and I've always replied to them politely 
1. Its not a big community we operate in.
2. They genuinely do not know the value of the cel
3. They simply may be taking an opportunistic 
chance at lowballing the price. (fair cop)
4. Cels prices are all over the show....and move 
all over the show - X/1999 cels being a classic 
case - note the vast price difference even across 
dealer sites for this series.
More and more I am certain that the value of the 
cel is only determined by what its worth to 
you.... I may be willing to pay prices on certain 
series that other collector give me the "are you 
insane look?" and other collectors are willing 
pay gormless sums on a series I detest.
Cels from certain series are worth much more to 
me than to other collectors and vice versa.

I've also emailed some other collectors and made 
offers for cels. I don;t do this often and 
particularly when the cels are not in the "make 
an offer" or for sale section, I assume that the 
collector will not sell unless I offer a premium. 
Sometimes however, since I do not know what a 
collector paid for a cel - I've come under their 
costs significantly. I've been embarressed but 
luckily the collectors who have come back have 
all been polite.