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: The coin has been auctioned 77 times, of which it has sold 70 times. This suggests good demand and sustained interest in the coin.

3. Previous Prices: By looking at previous auction prices for coins with a similar condition (80), we can see that the hammer prices have varied. For example:
- In a 2020 auction, a coin with a condition of 80 sold for 75 euros.
- In another auction in 2022, a coin with a condition of 80 sold for 100 euros.

4. Average Hammer Price: The average hammer price for this coin is 58.22 euros, providing an additional benchmark.

5. Starting Price: The starting price is 30 euros, indicating that the seller expects a lower price initially, but this does not necessarily reflect the true value of the coin.

Taking all these factors into account, an estimated maximum purchase price could be between 80 and 100 euros, given that there are examples of previous auctions in this range and the coin's condition is good. Therefore, a reasonable maximum purchase price could be 90 euros.