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

1. Current Condition: The coin has a condition of 80 (MS+). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for similar coins has been 755.83 euros.
- In previous auctions, coins with a similar condition (80) have had hammer prices ranging from 550 to 850 euros.
- The last auction with a condition of 80 had a hammer price of 600 euros.

3. Starting Price: The starting price is 600 euros, which is a good starting point. However, the hammer price is usually higher than the starting price.

4. Price Trends: In recent auctions, hammer prices have shown a trend of increasing, especially for coins in good condition.

5. Comparison with Previous Prices: In the past, coins with similar conditions have reached hammer prices of up to 850 euros.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 850 euros, as this price reflects both the current condition and the hammer price history in previous auctions.