Based on the data provided, we can observe that the coin in question has had an average starting price of 23.7 euros in previous auctions, with an average closing price of 36.79 euros. The condition of this coin has been described as 90 (EBC), indicating that it is in fairly good condition.

Additionally, several closing prices have been recorded in previous auctions, ranging from 27 euros to 40 euros. The estimated price in one of the auctions was 65.94 euros, suggesting that there is interest in this coin and its value can vary significantly depending on various factors.

Given that the coin will be auctioned with a starting price of 30 euros and considering its price history, condition, and demand, a maximum estimated purchase price could be around 45-50 euros. This range takes into account both the average closing price in previous auctions and the possibility that the coin's value may remain stable or even increase due to its condition and past demand.