It's unfortunate that things have to turn out 
this way, but a slight increase in the price due 
to changes in the exchange rate isn't the end of 
the world.  I know it's a bit frustrating 
(especially if your original money is still tied 
up with the postal service), but in the end it's 
just a small sacrifice to get the cel you want.

Similar events have occurred to me in the past.  
No matter how irritating these mix-ups can be, I 
just rationalize going through with the second 
payment this way:

[1] In cel collecting, a person will always 
makes a spending decision that they regret once 
in a while... no matter how hard you try to 
avoid doing so, it'll eventually happen.  But 
those are only minor bumps in the life of a cel 
collector (unless you agonize over them 
needlessly).  It's usually better just to take 
the minor hit and move on.

[2] If the dealer is someone I expect to do 
business with regularly or some time again in 
the future, I will go through with their wishes 
(as long as they are not being too unreasonable) 
in order to build up that relationship.  
Especially with dealers in Japan, they value 
returning customers that they can trust.

If you feel unjustly pressured into overpaying 
(which I don't think is the case, but I don't 
know the details) and you're willing to cease 
any business with this dealer, then I suppose 
you have the option of cancelling.

The only other thing I will say is that since 
the dealer forgot and misplaced your cel, that's 
a small cause for concern.  But many reputable 
dealers have made these kinds of mistakes in the 
past, so I don't think you should worry about 
that.  However, if this becomes a regular 
occurrence, you may reconsider sending more 
money to him/her.

I would prefer not to get too involved, but if 
you are not familar with the dealer, you can e-
mail me about them.  I'll try to let you know 
about their reputation (as far as I know about 
it).  But do not post that information on this 
board, for the sake of courtesy.