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

1. Coin Condition: The coin has a condition of 70 (MS-), which indicates that it is in acceptable shape, but not of high quality. This generally affects the price, as coins in better condition tend to fetch higher prices.

2. Auction History: By observing the hammer prices of coins with a similar condition (70) in the past, we can see that they have reached varying hammer prices. For example, in previous auctions, coins with a condition of 70 have had hammer prices ranging between 20 and 30 euros.

3. Average Hammer Price: The average hammer price for this particular coin is 98.74 euros, but this includes coins of different conditions. Given that the condition of this coin is 70, it is likely that the actual hammer price will be below this average.

4. Starting Price and Previous Prices: The current starting price is 15 euros, and the average starting price in the past has been 65.9 euros. However, the hammer prices of similar coins have been lower, suggesting that the starting price may be a good indicator of what to expect.

5. Recent Trends: In the most recent auctions, the hammer prices for coins with similar conditions have been in the range of 20 to 30 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 25 and 35 euros. This reflects a balance between the condition of the coin and the historical hammer prices for similar coins.