Others could tell you about the worth of the cel 
itself better than I can. :o) But the value of 
the fact that it's framed depends.

What kind of frame is it? Is it an off-the-rack 
$10 frame from Hobby Lobby? Or is it a $12/sq ft 
custom frame? Is it matted? How about double-or-
triple matted? What kind of glass was used? Is it 
UV-protected? Did they take it to Michaels or 
MJD, and have some high school kid permanently 
glue the cel to gatorfoam when they framed it? 
Were archival-quality materials used? Was any 
part of the cel damaged when it was framed? Was 
it framed by an art gallery (ie, professionals) 
or by a hobby shop?

In other words, being framed isn't necessarily a 
bonus. It might cause your shipping expenses to 
be higher in the end, if this is an item that 
will be going through the mail. But while I might 
charge someone part of the value of my $200 frame 
job, I'd absorb the cost of a $10 frame. You 
might ask about just buying the cel and sketch 
themselves.

-Cres