Based on the provided data, we can observe that the coin in question has a grade of 80 (MBC+), indicating that it is in fairly good condition. Additionally, it has been auctioned several times in the past, with varying starting and final prices.

The average starting price of previous auctions was 111.67 euros, while the average final price was 220 euros. In the last recorded auction, the coin was sold for 320 euros, surpassing the estimated price of 300 euros.

Taking these data into consideration, as well as the upcoming auction of the coin, we could estimate a maximum purchase price around 350-400 euros, considering the upward trend in final prices and the interest it has generated in previous auctions. It is important to note that the final price will depend on the demand at the auction and the competition from other potential buyers.