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+), indicating that it is in relatively good shape. This suggests that its value should be in a higher range compared to coins with lower conditions.

2. Auction History:
- The average hammer price from previous auctions is 279.29 euros, indicating that, in general, coins of this reference tend to sell for a considerably higher price than the starting price.
- The last auction in which a coin with a similar condition (80) was sold had a hammer price of 575 euros, which is a strong indicator that the market is willing to pay high prices for coins in good condition.

3. Starting and Hammer Prices:
- The current starting price is 150 euros, which is quite low compared to previous hammer prices. This could indicate a good buying opportunity.
- Previous hammer prices for similar conditions (75-85) have reached up to 570 euros, suggesting that the hammer price could be significantly higher than the starting price.

4. Sales Trends: The coin has been auctioned 9 times, of which 7 have sold. This indicates good demand in the market.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 600 euros, considering that the condition is good and that the hammer price history supports this estimate. A more conservative price could be around 500 euros, as it is an intermediate value between the average hammer price and the price of the last successful auction.