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 80 (MS+). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Auction Prices: By looking at previous auction prices for coins with a similar condition (80), we can see that they have reached auction prices that vary, but many are in the range of 300 to 650 euros. For example:
- In previous auctions, coins with a condition of 80 have reached hammer prices of 360, 440, 320, 421, etc.

3. Average Hammer Price: The average hammer price for this coin is 458.94 euros, which can also serve as a reference.

4. Starting Price: The current starting price is 150 euros, indicating that there is considerable room for the hammer price to rise.

5. Auction Trends: The coin has been auctioned 89 times, of which 83 have sold. This indicates good demand and a history of successful sales.

Based on these factors, an estimated maximum purchase price could be in the range of 600 to 700 euros, considering that the condition is good and that the historical hammer prices for similar coins support this estimate. However, it is important to keep in mind that the final price may vary depending on competition in the auction and other market factors at the time of the auction.