To estimate a maximum purchase price for the coin in question, we will consider several factors based on the provided data:

1. Starting price: 500 euros.
2. Auction history: The coin has been auctioned 8 times and has sold on all occasions, indicating a constant interest in the coin.
3. Average hammer price: 465.5 euros, suggesting that, on average, coins of this reference sell close to this price.
4. Condition: There is no information about the condition of this coin, which may complicate the estimation. However, we can observe that in previous auctions, coins with high grades (such as 90 and 95) have reached significantly higher hammer prices (750 and 800 euros, respectively).

5. Previous prices:
- In 2020, a coin with a grade of 30 sold for 40 euros.
- In 2020, a coin with a grade of 95 sold for 800 euros.
- In 2017, a coin with a grade of 90 sold for 750 euros.
- In 2024, a coin with a grade of 80 sold for 250 euros.

Since there is no information about the condition of the current coin, it is prudent to consider a price range. Based on the average hammer price (465.5 euros) and the hammer prices of coins with high grades, we can estimate that the maximum purchase price could be in a higher range.

Estimation of the maximum purchase price:
- Considering the average hammer price and the interest in the coin, a reasonable maximum purchase price could be between 600 and 800 euros, depending on the demand at the auction and the possible condition of the coin.

Therefore, an estimated maximum purchase price could be 700 euros.