To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

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

2. Previous Auction Prices:
- In recent auctions with a similar condition (70), the hammer prices have been:
- 45 euros (2022-03-16)
- 25 euros (2022-05-31)
- 29 euros (2023-01-18)
- 45 euros (2024-07-11)
- The highest hammer price in this condition range is 45 euros.

3. Price Trends:
- The average hammer price in the past has been 29.1 euros, suggesting that, although there are peaks, most sales have occurred in a lower range.

4. Starting Price: The current starting price is 18 euros, which is relatively low compared to previous hammer prices.

5. Estimation: Given that the condition is good and there are examples of previous auctions reaching up to 45 euros, a reasonable maximum purchase price could be in the range of 40 to 45 euros, considering that the market can fluctuate and demand may vary.

Conclusion: An estimated maximum purchase price for this coin could be 40 to 45 euros.