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. Auction History:
- The average hammer price for similar coins in the past is 39.46 euros.
- In previous auctions, hammer prices of up to 90 euros have been reached for coins with similar conditions (for example, in the auction on October 21, 2020).
- The last auction had a starting price of 40 euros and an estimated price of 70 euros, suggesting significant interest in this coin.

3. Price Trends:
- The current starting price is 40 euros, which is higher than the average starting price of 22.94 euros, indicating that the market is valuing this coin more than in the past.
- The price trend in recent auctions shows that coins with a condition rating of 80 have reached hammer prices around 40-80 euros.

4. Supply and Demand:
- Given that there is an auction scheduled in the coming days and considering that there have been 36 previous auctions, demand appears to be steady.

Based on these factors, an estimated maximum purchase price for this coin could be between 70 and 90 euros, as it has reached hammer prices in that range in the past and considering its good condition.

Therefore, a reasonable maximum purchase price could be 80 euros.