Based on the data provided, we can observe that the coin has had an average auction closing price of 41.09 euros in previous auctions. Additionally, the condition of the coin on this occasion is 75 (VF).

Considering that the starting price in this auction is 18 euros and the average closing price in previous auctions has been 41.09 euros, we could estimate a maximum purchase price around that value. However, taking into account that the condition of the coin is 75 (VF), which is a medium-fine condition, we could adjust that estimated price downwards.

Given that the coin has been sold in the past for prices ranging between 25 and 50 euros, and considering the current condition, we could estimate a maximum purchase price around 35-40 euros.

Therefore, my recommendation would be to consider a maximum purchase price of around 35-40 euros for this coin in the current auction.