Based on the data provided, we can observe that the coin has had an average auction closing price of 32.35 euros in previous auctions. Additionally, the current condition of the coin is 30 (BC+).

Considering that the coin will be auctioned in the upcoming days with a starting price of 18 euros and an estimated price of 16.89 euros, and taking into account that in previous auctions it has reached prices of up to 180 euros in conditions of conservation of 85 (FDC), we can estimate a maximum purchase price for this coin in the next auction.

Given that the coin has been sold in the past for prices ranging between 9 and 180 euros, and considering its current condition of 30 (BC+), we could consider a maximum estimated purchase price around 40-50 euros.

It is important to note that the final auction price will depend on several factors, such as the demand at that specific moment, the competition from other bidders, and the buyer's willingness to pay for that particular piece.