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 condition but not of high quality. This will affect the maximum price that can be offered.

2. Auction History: By observing previous hammer prices for coins with a similar condition (70), we can see that hammer prices have varied. For example:
- In previous auctions, coins with a condition of 70 have reached hammer prices ranging from 14 to 45 euros.
- The average hammer price for coins of similar condition seems to be around 30-40 euros.

3. Starting Price and Previous Hammer Prices: The current starting price is 15 euros, and the average hammer price in the past has been 49.04 euros. However, given that the condition is 70, it is likely that the hammer price will not reach the highest average.

4. Recent Trends: In the most recent auctions, hammer prices for coins of similar condition have been in the range of 25 to 35 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 30 and 40 euros, considering that the condition and price history suggest that this range should not be exceeded to ensure a reasonable purchase.

Therefore, a reasonable maximum purchase price could be 35 euros.