We will never know the other bids. So we don’t know if your advice was better than their Realtor’s. All we know is that they “won”. All other bids remain secret. For all anybody knows, their bid might have been 10% higher than anyone else. So they maybe “overpaid” by $100,000. We will never know.
Spring of 2016. There is a home listed in Saanich for $899,000. Two offers including my clients. My clients offered $935,000 and we see the property pending (sold) a couple of days later for $1,105,000. The other party incorrectly guessed my clients were bidding around $1.1 and overpaid by $170k.
On my listings I've had a number of situations in the last 24 months where the winning bid is 100k, or more, above the second highest bid.
You are correct in that the bids are kept confidential, we don't release them and why would we. A lot of buyers would be very upset by the amount they overpaid. Usually you call back the winning offer agent and say something like "my clients absolutely loved your clients letter, congratulations." You aren't going to tell them that they way overpaid.