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

1. Coin 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. Current and Previous Prices: The current starting price is 150 euros. In the past, coins with a similar condition (85) have had auction prices that varied, but there are examples of auctions reaching up to 320 euros (as seen in the auction on 2018-10-17).

3. Price Trends: The average auction price for similar coins is 94.76 euros, but there are examples of higher auction prices, especially for coins in better condition.

4. Auction Frequency: The coin has been auctioned 89 times, with a 74% sell-through rate, indicating consistent interest in this coin.

5. Recent Auction Prices: In recent auctions, the hammer prices have varied, but there are examples of auctions exceeding 200 euros for coins in similar condition.

Based on these factors, an estimated maximum purchase price could be in the range of 200 to 300 euros, considering that the condition is good and there are precedents for higher hammer prices in the past.

Therefore, a reasonable maximum purchase price could be 250 euros.