Are the auctions for unusual or hard to find items?
I tend to think so if you are looking for them overseas.
And that also makes me tend to think that others may be doing the same.
Sometimes even the worldwide pool of collectors is very small.
Still Bid Once Bid Your Maximum.
Then you cannot pay more than you are willing to pay.
And remember if someone beats your maximum bid, he was not shilling, he just has deeper pockets than you do.