Based on the data provided, we can observe that the coin has had an average auction price of 67.61 euros in the past. Additionally, the condition of the coin in this auction is 30 (BC+).

Previous prices for this coin have ranged between 12 euros and 140 euros, depending on factors such as condition and demand at that time.

Given that the coin will be auctioned with a starting price of 18 euros and considering its price history, condition, and demand, we could estimate a maximum purchase price around 100 euros. This price aligns with previous auction prices and takes into account the current condition of the coin.

It is important to note that the final auction price may vary depending on the competition from other bidders interested in the coin in question.