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 quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous Prices: By looking at previous auction prices for coins with similar conditions, we can see that the auction price has varied. For example:
- In 2023, a coin with a condition of 95 was auctioned for 340 euros.
- In 2022, a coin with a condition of 85 was auctioned for 150 euros.
- In 2019, a coin with a condition of 80 was auctioned for 260 euros.

3. Average Auction Price: The average auction price for this coin is 290.14 euros, which gives us a good reference for what buyers are willing to pay.

4. Starting Price and Average Starting Price: The current starting price is 150 euros, and the average starting price is 192.79 euros. This suggests that the starting price is relatively low compared to the average auction price.

5. Recent Trends: The trend in auction prices has been upward in recent years, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price could be in the range of 300 to 350 euros, considering that the condition is good and the average auction price is 290.14 euros. This also takes into account the possibility that buyers may be willing to pay a bit more for a coin in superior condition.

Therefore, a reasonable maximum purchase price could be 350 euros.