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

1. Coin Condition: The coin has a condition rating 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 a similar condition (80), we can see that the hammer prices have varied. For example:
- In previous auctions, coins with a condition of 80 have reached hammer prices of 60, 55, 120, and 45 euros, among others.
- The average hammer price for coins of similar condition seems to be in the range of 60 to 120 euros.

3. Starting Price and Average Hammer Price: The current starting price is 30 euros, and the average hammer price in the past has been 81.91 euros. This suggests that the hammer price could be significantly higher than the starting price.

4. Recent Trends: In the most recent auctions, the hammer price for coins of similar condition has shown a range of 60 to 90 euros, which also supports the idea that the hammer price could be higher.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 90 to 120 euros. This is based on the historical hammer prices for coins of similar condition and the current state of the coin. However, it is important to note that the final price may vary depending on demand at the auction and other market factors.