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

1. Current Condition: The coin has a condition of 80 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History: By looking at previous hammer prices for coins with similar conditions, we can see that:
- In past auctions, coins with a condition of 80 have reached hammer prices of up to 85 euros.
- The average hammer price for coins with conditions of 80 and 90 has been approximately 60-85 euros.

3. Average Hammer Price: The average hammer price for this particular coin is 45.8 euros, which gives us a reference for what buyers have been willing to pay in the past.

4. Starting Price and Estimates: The current starting price is 30 euros, and the average starting price in the past has been 33.33 euros. This suggests that the market is willing to accept a higher starting price.

5. Recent Trends: In the most recent auctions, hammer prices have shown a trend of increasing, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price for this coin could be between 70 and 90 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate. Therefore, a reasonable maximum purchase price could be 85 euros.