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 85 (ebc-), 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 in the past has been 56.73 euros.
- The coin has been auctioned 27 times, of which 22 have been successful sales. This suggests there is consistent interest in this coin.
- Previous hammer prices for coins with similar conditions (around 80-85) have varied, but some have reached up to 140 euros in optimal conditions.

3. Starting Price and Average Starting Price:
- The current starting price is 30 euros, and the average starting price in the past has been 27.6 euros. This indicates that the current starting price is reasonable and could attract bidders.

4. Price Trends:
- In previous auctions, hammer prices have shown a considerable range, but generally, coins in similar conditions have reached hammer prices that exceed the starting price.

Based on these factors, an estimated maximum purchase price could be in the range of 70 to 90 euros, considering that the condition is good and that interest in the coin has been consistent. This also takes into account that the average hammer price has been 56.73 euros, suggesting that bidders are willing to pay more than the starting price under favorable conditions.

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