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 estimated prices.

The average starting price of previous auctions was 28.4 euros, while the average final price was 31.86 euros. In the last recorded auction, the coin was sold for 90 euros, significantly exceeding the estimated price.

Taking into account this data, as well as the history of previous prices, we could estimate a maximum purchase price for this coin in the next auction. Given the coin's strong performance in previous auctions and its grade of 80 (MBC+), we could suggest a maximum purchase price around 100-110 euros. This estimation is based on the upward trend in final prices and the good condition of the coin.

It is important to consider that the final auction price will depend on various factors, such as demand at that specific time, competition from other bidders, and buyers' willingness to pay a higher price for this particular coin.