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

1. Starting price: 60 euros.
2. Condition: The coin has a condition rating of 80 (VF+), indicating that it is in quite good shape.
3. Auction history: It has been auctioned once in the past and sold on that occasion, suggesting there is interest in the coin.
4. Average hammer price: 340 euros, which is significantly higher than the starting price.

Given that the average hammer price is 340 euros and considering that the condition is good, we could estimate that the maximum purchase price might be in a range close to this average price, but not necessarily equal, since the starting price is 60 euros.

Taking all these factors into account, an estimated maximum purchase price could be between 300 and 350 euros, depending on the demand at the auction and the interest from collectors.

Therefore, a reasonable maximum purchase price could be 350 euros.