To estimate a maximum purchase price for the coin in question, we can analyze the provided data and make some comparisons.

1. Current Condition: The coin has a condition of 75 (MS). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Auction Prices:
- In 2014, a coin with a condition of 80 sold for 4200 euros.
- In 2024, a coin with a condition of 90 sold for 9500 euros.
- Overall, the hammer prices have been significantly higher than the starting prices.

3. Average Hammer Price: The average hammer price for similar coins is 6740 euros, indicating that there is a market willing to pay high prices for coins of this reference.

4. Price Trends: Observing the starting and hammer prices, it seems that coins with higher conditions have reached hammer prices that are approximately 2-3 times their starting price.

Given that the condition of the coin in question is 75, which is lower than the conditions of the coins that have sold for higher prices, we can adjust our expectations.

### Estimated Maximum Purchase Price:
- Considering that the starting price is 1500 euros and the average hammer price is 6740 euros, we could estimate that the hammer price for a coin with a condition of 75 might be in a lower range than the average, but still considerably higher than the starting price.
- A reasonable approach would be to consider a hammer price that could be between 2-3 times the starting price, adjusted for the condition.

Therefore, an estimated maximum purchase price could be in the range of 3000 to 4500 euros. This is based on previous price trends and the current condition of the coin.