Based on the data provided, we can observe that the coin has had an average auction closing price of 27.13 euros in previous auctions. Additionally, the condition of the coin on this occasion is 75 (VF).

Considering that the coin will be auctioned in the coming days with a starting price of 18 euros and has had an average starting price of 20.34 euros in the past, we can estimate that the closing price could be around 27.13 euros, which is the historical average closing price.

Given that the condition of the coin is 75 (VF), which is in an acceptable condition, and taking into account the history of previous closing prices, we could estimate a maximum purchase price of around 27 euros for this coin in the next auction.