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 75 (MBC), indicating that it is in fairly good shape, but not the best possible condition.

2. Auction History:
- The average hammer price for similar coins has been 46.07 euros.
- In previous auctions, hammer prices have varied, but there are examples of coins with similar conditions that have sold for prices ranging from 12 to 340 euros, depending on the condition and demand.

3. Starting Price and Estimates:
- The current starting price is 15 euros, and the average starting price in the past has been 21.6 euros.
- The estimated price for this auction is 25 euros, suggesting that there are expectations for the coin to sell for a reasonable price.

4. Sales Trends:
- Of the 20 times it has been auctioned in the past, it has sold 16 times, indicating a good sales rate.

Based on these factors, an estimated maximum purchase price could be around 40-50 euros, considering that the condition is good and that the average hammer price in the past has been 46.07 euros. This also takes into account the possibility that demand may vary in the current auction.

Therefore, a reasonable maximum purchase price could be 50 euros.