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

1. Current Condition: The coin has a condition 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 Auction Prices: By observing previous auction prices for coins with similar conditions (around 75-85), we can see that auction prices have varied. For example:
- In previous auctions, coins with a condition of 75 have reached auction prices of up to 65 euros.
- Coins with a condition of 80 have reached auction prices of up to 120 euros.

3. Average Auction Price: The average auction price for this coin is 52.02 euros, providing a baseline for estimation.

4. Recent Trends: The coin has been auctioned 80 times in the past, with an 86.25% sell-through rate (69 out of 80). This suggests consistent demand.

5. Starting Price and Average Starting Price: The current starting price is 30 euros, and the average starting price is 31.39 euros. This indicates that the starting price is reasonable compared to the market.

Based on these factors, an estimated maximum purchase price for the coin could be between 80 and 120 euros, considering its good condition and the price trends in previous auctions. An auction price of 100 euros could be a reasonable target, as it aligns with the auction prices of coins with similar conditions in the past.