It's an all too common practice and I really don't like it...excessively high estimates in coin auctions.
below is an example in a current auction. It is an unexceptional VLPP from Siscia (RIC 84). The starting bid is $240 and it is estimated at $400.
Is this merely greed or lack of knowledge of a realistic value-- or maybe a combination of both.
On a really good day, I would be surprised if this coin sold in the $40-50 range. If it did not have the encrustations, maybe $100- 150.