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

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

2. Previous Prices: By looking at the auction prices of coins with similar grades (75-80), we can see that the hammer prices have varied. For example:
- In previous auctions, coins with a grade of 75 have reached hammer prices of up to 60 euros.
- Coins with a grade of 80 have reached hammer prices of up to 110 euros.

3. Average Hammer Price: The average hammer price for this coin is 60.04 euros, which gives us a good reference.

4. Recent Trends: In the most recent auctions, hammer prices have shown an increase, especially for coins in good condition. For example, in a recent auction, a coin with a grade of 90 sold for 190 euros.

5. Starting Price: The starting price is 15 euros, indicating that there is considerable room for the hammer price to be higher.

Based on these factors, an estimated maximum purchase price for the coin with a grade of 75 could be between 70 and 90 euros, considering that the market may be willing to pay more for coins in good condition and that there is an upward trend in hammer prices.

Therefore, a reasonable maximum purchase price could be 80 euros.