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

1. Current Condition: The coin has a condition rating of 80 (MBC+), which is quite good. In the past, coins with a similar condition have reached auction prices of up to 3600 euros.

2. Auction History:
- The average hammer price for previous auctions of this coin is 2671.43 euros.
- The last auction in March 2023, with a condition rating of 90, reached a hammer price of 4200 euros, indicating that the market is willing to pay more for coins in better condition.

3. Starting Price and Estimates:
- The current starting price is 1500 euros, which is reasonable compared to the average starting price of 1311.11 euros.
- The estimated hammer price for this auction is 2000 euros, suggesting that there are expectations for the coin to sell for a price higher than the starting price.

4. Market Trends: Since the coin has sold in 7 of the last 8 auctions, there is good demand. Additionally, the fact that it will be auctioned again soon may increase interest.

Based on these factors, an estimated maximum purchase price could be in the range of 2500 to 3000 euros. This is based on the auction price history for coins of similar condition and market trends. However, it is important to consider that the final price may vary depending on competition in the auction and the interest of other buyers.