Based on the provided data, we can observe that the coin in question had a starting price of 25 euros in the most recent auction, with a conservation value of 30 (BC+). Additionally, it has been auctioned in the past with starting prices ranging from 12 to 60 euros, estimated prices ranging from 20 to 100 euros, and final auction prices ranging from 12 to 60 euros.

Considering that the historical average final auction price is 35.34 euros and the coin is in a conservation state of 30 (BC+), we could estimate a maximum purchase price around 40-45 euros. However, keep in mind that the final auction price may vary depending on the demand at that specific moment.

In summary, an estimated maximum purchase price for this coin in the next auction could be around 40-45 euros.