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-). This indicates that it is in an acceptable state, but not of high quality. Coins with a higher condition tend to reach higher prices at auctions.

2. Auction History:
- The average hammer price for similar coins in the past has been 114.02 euros.
- The coin has been auctioned 63 times, of which it has sold 57 times, indicating good demand.
- Previous hammer prices for coins with similar conditions (70) have varied, but some examples are:
- 2022-11-16: Starting price 18, hammer price not available, condition 70.
- 2023-02-16: Starting price 40, hammer price 55, condition 70.
- 2024-07-11: Starting price 40, hammer price 75, condition 80.

3. Starting Price and Estimates:
- The current starting price is 18 euros, which is relatively low compared to the average hammer price.
- The average starting price for similar coins is 81.33 euros, suggesting that the current starting price may be underestimated.

4. Recent Trends:
- In the most recent auctions, hammer prices have shown a range that can be considerably higher than the starting price, especially for coins in similar conditions.

Based on these factors, an estimated maximum purchase price could be between 70 and 100 euros, considering that the condition is 70 and the average hammer price is 114.02 euros. This would allow for a competitive offer without exceeding the expected market value.