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), which indicates that it is in fairly good shape, but not the best possible condition.

2. Previous Auction Prices:
- In 2015, a coin with the same condition (75) sold for 1103.45 euros.
- In 2016, a coin with better condition (85) sold for 2598.18 euros.
- The starting and final prices in previous auctions varied significantly, indicating that interest and demand can influence the final price.

3. Average Starting and Final Prices:
- The average starting price is 369.49 euros, and the average final price is 1074.51 euros. This suggests that, in general, coins of this reference tend to reach final prices significantly higher than their starting price.

4. Sales Trends: The coin has sold in 4 out of the last 5 auctions, indicating a consistent interest in this reference.

Given all this, and considering that the condition of the coin is 75, an estimated maximum purchase price could be in a range between the average final price and the highest price reached in previous auctions.

Therefore, an estimated maximum purchase price could be around 1000 to 1200 euros. This is based on historical interest and the final prices of similar coins in comparable conditions.