If it's a rare item and it is unlikely for a seller to have two (or more), then your concerns about shilling are understandable.
It may be that the winning bidder was a real bidder with remorse.
It may be that the winning bidder was a shill.
Only eBay could check that out properly.
Or it may be that the seller did, indeed, have two items - but only put one up to see what bidding would have been made on it. If the final bid was low or it didn't sell, they would re-think how to sell the other one - but they may have been pleased with the result and happy to offer the second one for the price of the second-chance offer. I have a seller that has been in that situation on some rarer publications they have.
Also, see if their feedback gives any indication of dodginess.
As for your decision to buy - I can understand your caution even if you are comfortable with the seller. My approach is this:
- When I bid, I snipe, fully aware of the process of determining my bid price and following the philosophy "Bid for a win and hope for a bargain". If I get pushed to my maximum, then that's the risk I accepted.
- However, with a second chance offer, that risk no longer exists - it is now a certainty. I WILL pay my maximum. I then look at it as a BIN purchase and assess the asking price as such.
Hope this helps.