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

1. Starting price: 150 euros.
2. Average hammer price in the past: 340 euros. This indicates that, in general, coins of this reference tend to sell for a significantly higher price than their starting price.
3. Condition of the coin: 70 (VF-). This suggests that the coin is in good condition, which can positively influence its value.
4. Auction history: The coin has been auctioned once and sold on that occasion, indicating that there is interest in it.

Given that the average hammer price is 340 euros and considering that the condition is 70, which is quite good, we could estimate that the maximum purchase price could be in a range close to the average hammer price.

Therefore, an estimated maximum purchase price could be around 300-350 euros, taking into account that the starting price is 150 euros and that the interest in the coin may drive the hammer price closer to the historical average.