And if you make someone happy by letting him or 
her own a cel that s/he really wants to have and 
considers the price worth the rush of ownership, 
then you'd be foolish to refuse to sell it 
because to do so you'd turn a profit.

I hear what you're saying: that you're not in the 
hobby to make money, and doing so might 
compromise your personal collecting ethics.  But 
in this case, if you're ready to part with the 
cel and the buyer knows that comparable cels go 
for about what you're asking, and is OK with 
that, then you'd making him or her miserable by 
not concluding the deal.

And cels were created to make people happy, ne?