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

2. Current Starting Price and Previous Prices: The current starting price is 75 euros. In previous auctions, we have seen hammer prices that vary considerably, but there are examples of coins with similar conditions that have sold for higher prices. For example:
- In 2020, a coin with a condition of 85 sold for 140 euros.
- In 2019, a coin with a condition of 80 sold for 50 euros, but another with a condition of 90 sold for 110 euros.

3. Average Hammer Price: The average hammer price for this coin is 104.69 euros, suggesting that, in general, buyers are willing to pay more than the starting price.

4. Auction Trends: The coin has been auctioned 67 times, of which 55 resulted in sales. This indicates a consistent interest in the coin, which may influence the price.

5. Comparison with Estimated Prices: The estimated price for the coin in the current auction is 150 euros, suggesting that there are expectations for it to sell at a higher price.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 120 to 150 euros. This is based on the current condition, previous hammer prices, and general interest in the coin.

Therefore, a reasonable maximum purchase price could be 150 euros.