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

1. Current Condition: The coin has a condition of 70 (VF-), which indicates that it is in relatively good shape, but not of the best quality (UNC).

2. Auction History:
- The average hammer price in previous auctions is 24.27 euros.
- The hammer prices in previous auctions for coins with similar conditions (around 70) have varied, but there are examples of sales reaching up to 48 euros (such as in the 2020 auction with a condition of 80).

3. Starting Price and Average Starting Price:
- The current starting price is 15 euros, and the average starting price in the past has been 17.57 euros.

4. Sales Trends: The coin has been auctioned 15 times, of which it has sold 13 times, indicating good demand.

Based on this data, an estimated maximum purchase price could be in a range between the average hammer price (24.27 euros) and the highest price reached in previous auctions (48 euros). However, since the current condition is 70, it is reasonable to adjust downwards.

Therefore, an estimated maximum purchase price could be approximately 30-35 euros. This reflects a balance between the current condition, the price history, and the demand observed in previous auctions.