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

1. Current Condition: The coin has a condition of 85 (ebc-), which indicates that it is in fairly good shape, but not the best possible condition (which would be 110).

2. Historical Prices: By looking at previous auction prices for coins with similar conditions, we can see that prices have varied. For example:
- In 2012, a coin with a condition of 90 sold for 200 euros.
- In 2014, a coin with a condition of 90 sold for 168.62 euros.
- In 2016, a coin with a condition of 90 sold for 90 euros.

3. Average Auction Price: The average auction price for this coin is 74.43 euros, which can serve as a reference point.

4. Starting Price: The current starting price is 55 euros, which is lower than the average auction price.

5. Sales Trends: The coin has been auctioned 45 times, of which it has sold 27 times. This indicates a moderate interest in the coin.

Given all this, an estimated maximum purchase price could be in a range between the average auction price and a bit more, considering the condition and interest in the coin.

Final Estimate: A reasonable maximum purchase price could be around 90-100 euros. This is based on the current condition and the auction prices of similar coins in the past.