I don't have the links saved, but there have been 
cels that I was bidding on that I was outbid and 
then they appeared on Mangaya's next update. 
DB372 under Trunks was one, and so was DB374 also 
in the Trunks section. I distinctly remember 
seeing DB324, DB329, DB375 (which was sold by 
Lute826 (DB Cel Town) on YJ a couple of months 
ago).  I looked through Lute826's feedback to see 
if I could find the auction for the Vegeta #DB375 
and unfortunately could not find it.  But I've 
seen it happen repeatedly in the past. Either 
they are buying directly from Yahoo Japan and 
reselling (another thing to consider is that you 
can have multiple Yahoo ID's - I have 2 :P) or 
else someone they buy from is doing the buying 
from YJ and selling to them.  On a side note: 
there is someone who buys and resells from Yahoo 
Japan to Anime Taro... I've seen a ton of cels 
that have been purchased from the seller kerwein 
show up there. Specifically those purchased by 
the bidder keiniku6516. So maybe they're doing 
the same thing with Mangaya.