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-), indicating 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 looking at previous hammer prices for coins with similar conditions, we can see that:
- In past auctions, coins with a condition of 70 have reached hammer prices that vary, but are generally in the range of 20 to 45 euros.
- The last auction of a coin with a similar condition (70) had a hammer price of 26 euros.

3. Average Hammer Price: The average hammer price for this particular coin is 49.04 euros, but this may be influenced by coins in better condition.

4. Recent Trends: In the most recent auctions, hammer prices for coins with a condition of 70 have been around 20 to 35 euros.

5. Starting Price: The starting price is 15 euros, suggesting that the seller expects a reasonable price, but not necessarily a high one.

Based on these factors, an estimated maximum purchase price for this coin could be between 30 and 45 euros, considering that the condition is not the best and that the hammer price history for similar coins supports this estimate.

Therefore, a reasonable maximum purchase price could be 40 euros.