To estimate a maximum purchase price for the coin in question, we can analyze the provided data:

1. Current Condition: The coin has a condition of 75 (MBC), indicating that it is in quite good shape. This generally translates to a higher price compared to coins in lower condition.

2. Auction History:
- In 2015, the coin was auctioned with a starting price of 15 euros and sold for 17 euros.
- In 2014, it was auctioned with a starting price of 60 euros and sold for 65 euros.
- Also in 2014, another auction had a starting price of 18 euros and sold for 26 euros.

3. Average Prices: The average starting price is 30.75 euros and the average final price is 59.5 euros. This suggests that, in general, coins of this reference tend to sell for a price higher than the starting price.

4. Price Trends: Looking at previous final prices, the highest price was 65 euros, while the lowest was 17 euros. However, the average final price is 59.5 euros, indicating that, overall, coins of this reference are reaching higher prices in recent auctions.

Given that the condition of the coin is good (75), and considering the final price history, an estimated maximum purchase price could be positioned in a range between the average final price and the highest recorded price.

Estimated Maximum Purchase Price: It could be reasonable to estimate a maximum purchase price of around 70 euros, taking into account the good condition and the price history.