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

1. Current Condition: The coin has a condition rating of 85 (ebc-), indicating that it is in quite good shape. This suggests that its value should be above that of coins with lower conditions.

2. Previous Auction Prices: Looking at previous auction prices for coins with a similar condition (85), we find that:
- In 2020, a coin with a condition of 85 was auctioned for 45 euros.
- In 2020, another coin with a condition of 85 was auctioned for 75 euros.
- In 2022, a coin with a condition of 85 was auctioned for 85 euros.

3. Average Auction Price: The average auction price for all auctions of this coin is 160.25 euros, indicating that there is potential for a higher value, especially if the condition is good.

4. Starting Price and Average Starting Price: The current starting price is 90 euros, and the average starting price in the past has been 78.66 euros. This suggests that the current starting price is reasonable and could attract buyers.

5. Market Trends: Since the coin has been auctioned 38 times and sold 30 times, there is consistent interest in this coin, which may increase its value.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 200 euros, considering that the condition is good and there are precedents for higher auction prices in the past. However, given the starting price of 90 euros, it is likely that buyers would be willing to pay a bit more, but not necessarily reaching the average auction price of 160.25 euros.

Therefore, a reasonable maximum purchase price could be 180 euros.