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

1. Current Condition: The coin has a condition of 70 (VF-), which is a medium level. This suggests that its value will not be as high as that of coins in better condition.

2. Auction History:
- In the past, the coin has been auctioned 5 times and has sold in all of them, indicating a consistent interest in the coin.
- Previous hammer prices for coins with a similar condition (70) have ranged from 280 to 380 euros.

3. Starting Price and Average Price:
- The current starting price is 225 euros, which is below the average starting price of 233.33 euros.
- The average hammer price is 328 euros, suggesting that the final price could be in a similar range.

4. Price Trends:
- In previous auctions, hammer prices for coins with a condition of 70 have been in the range of 280 to 380 euros. This suggests that the final price could be at the upper end of this range, given that interest in the coin appears to be strong.

Based on these factors, an estimated maximum purchase price could be around 350 euros, considering that it is a reasonable price based on previous auctions and the current condition of the coin.