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

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 45.17 euros.
- The last auction for a coin with a similar condition (80) had a hammer price of 40 euros.
- In previous auctions, hammer prices for coins with a condition of 80 have ranged between 25 and 60 euros.

3. Starting Price: The starting price for this auction is 40 euros, which is a good starting point.

4. Price Trends: Observing previous hammer prices, it seems there is a trend for coins with a condition of 80 to sell in a range of 30 to 60 euros, with some exceptional cases reaching up to 70 euros.

Based on these factors, an estimated maximum purchase price for this coin could be around 60-70 euros, considering that the condition is good and that interest in the coin may be high. However, since the starting price is 40 euros, it is likely that the hammer price will not significantly exceed this value unless there is strong competition among bidders.

Therefore, a reasonable maximum purchase price could be 65 euros.