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

1. Coin Condition: The coin has a condition of 70 (MBC-). This indicates that it is in an acceptable state, but not of high quality. In comparison to other auctioned coins, those with a higher condition tend to reach higher prices.

2. Previous Prices: By observing the hammer prices of coins with similar conditions (around 70), we can see that the hammer prices have varied. For example, in previous auctions, coins with a condition of 70 have reached hammer prices ranging from 16 to 76 euros.

3. Average Hammer Price: The average hammer price for this coin is 116.27 euros, but this may be influenced by coins in better condition.

4. Starting Price and Estimates: The starting price is 15 euros, and the average starting price is 80.21 euros. This suggests that there is potential for an increase in the hammer price.

5. Auction Trends: Since it has been auctioned 81 times and sold 66 times, there is good demand for this coin, which may increase its price.

Based on these factors, an estimated maximum purchase price could be in the range of 50 to 80 euros, considering that the condition is 70 and that the hammer price may vary depending on competition in the auction. However, given the price history and demand, a reasonable maximum purchase price could be approximately 70 euros.