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

1. Current Condition: The coin has a condition of 75 (MBC), indicating that it is in fairly good shape, but not the best possible condition.

2. Auction History:
- The average hammer price for similar coins has been 7726.22 euros.
- In previous auctions, coins with a condition of 75 have reached hammer prices of 2750 euros (2011) and 8000 euros (2013).
- Coins with higher conditions (90) have also sold for higher prices, such as 5500 euros and 8000 euros.

3. Starting Price: The current starting price is 3000 euros, which may indicate a minimum expected price.

4. Sales Trends: The coin has been auctioned 7 times, of which 6 have sold, indicating a consistent interest in this reference.

5. Comparison with Previous Prices: Previous hammer prices for similar conditions suggest that the price could range between 2750 and 8000 euros, depending on demand at the auction.

Based on these factors, an estimated maximum purchase price could be in the range of 6000 to 8000 euros, considering that the condition is good and there is a history of hammer prices supporting this estimate. However, since the condition is not the highest, a more conservative price could be around 6000 euros.

Therefore, a reasonable estimated maximum purchase price could be 7000 euros.