To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

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

2. Historical Prices: Looking at previous auction prices for coins with a similar condition (80), the highest auction price was 90 euros in December 2020. There are also other auctions in the range of 45 to 90 euros.

3. Average Auction Price: The average auction price for this coin is 88.94 euros, suggesting that, in general, buyers are willing to pay close to this price.

4. Starting Price and Average Starting Price: The current starting price is 25 euros, and the average starting price is 45.28 euros. This indicates that the current starting price is relatively low compared to the average starting price.

5. Sales Trends: The coin has been auctioned 41 times, of which 36 have been sold. This suggests that there is consistent interest in this coin, which may influence the price.

Given all this, an estimated maximum purchase price for the coin could be in the range of 80 to 100 euros, considering that the condition is good and the average auction price is close to 90 euros. However, to be more conservative and taking into account the variability in auctions, a reasonable maximum purchase price could be 90 euros.