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 an acceptable state, but not among the best qualities.

2. Historical Prices: By observing the hammer prices of coins with similar conditions (around 75-80), we can see that the hammer prices have varied. For example:
- In previous auctions, coins with a condition of 80 have reached hammer prices of up to 90-120 euros.
- Coins with a condition of 75 have had hammer prices ranging between 30 and 70 euros.

3. Average Hammer Price: The average hammer price for this coin is 84.28 euros, which gives us a good reference for what buyers are willing to pay.

4. Recent Trends: In the most recent auctions, hammer prices for coins of similar condition have shown a range of 30 to 90 euros, depending on demand and supply at the time of the auction.

5. Starting Price: The starting price is 18 euros, suggesting that there is considerable room for the hammer price to be higher.

Based on these factors, an estimated maximum purchase price for this coin could be between 80 and 120 euros, considering that the condition is good and there is interest in the coin. However, since the condition is not the highest, a more conservative price could be around 90 euros as a reasonable upper limit.