Based on the data provided, we can observe that the coin in question has had an average auction closing price of 20.83 euros in previous auctions. Additionally, its current condition is 95 (EBC+), indicating that it is in quite good condition.

Considering that the starting price in the upcoming auction will be 30 euros and the historical average closing price is 20.83 euros, we can estimate that the closing price will likely be in a range close to these values.

Given that the coin has performed well in previous auctions and its condition is high, we could expect the closing price to be around 25-30 euros on this occasion.

Therefore, my estimate for the maximum purchase price for this coin in the next auction would be around 30 euros.