If he sent you the $50, you should send him one 
of the nice A1 cels and the 2 cheap ones. You 
should at least try to honor your deal in the 
best way possible and show that you made an 
effort to be fair. Regardless of his sales 
record, you shouldn't be the one to punish him. 
Even if it is a B13 cel, with the whole setup it 
is still a $500-$600 package easy. If you want, 
you can send him your least favorite A1 cel. Just 
a suggestion, but in my opinion you got a very 
good deal and should do the right thing.