To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Coin Condition: The coin has a condition rating of 80 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous Prices: By looking at the auction prices of coins with similar conditions (around 80), we can see that auction prices have varied, but there are examples of auctions reaching up to 60 euros for coins in similar conditions.

3. Average Auction Price: The average auction price for this coin is 46.83 euros, which is also a good indicator of the expected value.

4. Recent Trends: In the most recent auctions, the auction prices for coins with similar conditions have been in the range of 30 to 60 euros.

5. Starting Price: The starting price is 15 euros, suggesting that there is considerable room for the final auction price to be higher.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 60-70 euros. This is based on the analysis of previous prices, the condition of the coin, and current market trends.