Based on the data provided, we can see that the coin in question had a starting price in the current auction of 18 euros, with a historical average starting price of 10.04 euros and a historical average selling price of 21.13 euros. The coin's condition is 100 (Uncirculated).

Additionally, several auctions have been conducted in the past, with varying starting, estimated, and selling prices. The highest estimated price was 30 euros and the highest selling price was 65 euros.

Considering these data, as well as the upward trend in selling prices, and taking into account the high condition of the coin, we could estimate a maximum purchase price of around 35-40 euros. This is considering that the highest historical selling price was 65 euros and that the coin is in excellent condition.