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

1. Current Condition: The coin has a condition of 70 (VF-), which indicates that it is in an acceptable state, but not of high quality. This may influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price for similar coins is 114.62 euros.
- In the past, coins with similar conditions (70) have reached hammer prices of 35 euros (2018) and 40 euros (2021).
- The last auction of a coin with a condition of 70 had a hammer price of 40 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 25 euros, which is below the average starting price of 72.81 euros. This suggests there is potential for an increase in the hammer price.

4. Sales Trends: Out of the 17 times it has been auctioned, 13 have been sold, indicating a good sales rate.

Based on these factors, an estimated maximum purchase price could be in the range of 40 to 60 euros, considering that the average hammer price for coins of similar condition has been 40 euros and that the overall average hammer price is 114.62 euros, but adjusted for the current condition.

Therefore, a reasonable estimated maximum purchase price could be 50 euros.