Based on the data provided, we can observe that the coin has had an average auction price of 646.1 euros in the past. Additionally, it has been auctioned 25 times and sold in 22 of those auctions.

The current condition of the coin is 25 (BC), indicating that it is not in the best condition, but it is not extremely deteriorated either.

Reviewing the previous prices of the coin, we can see that it has had auction prices ranging from 116 euros to 3600 euros, with estimates ranging from 50 euros to 2500 euros.

Given that the coin has sold in the majority of past auctions and has had auction prices significantly higher than the current starting price (30 euros), we could estimate a maximum purchase price in the range of 600 to 800 euros, considering the current condition and auction price history.

Therefore, an estimated maximum purchase price for this coin in the next auction could be around 700 euros.