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 a fairly good state. This suggests that its value could be in the upper range of previous auctions.

2. Auction History:
- The average hammer price in previous auctions is 70.75 euros.
- The last auction with a known hammer price was 100 euros for a coin with a condition of 80.
- Generally, hammer prices for coins with similar conditions (70-80) have ranged between 55 and 120 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 40 euros, which is slightly below the average starting price of 41.27 euros. This could indicate that there is a buying opportunity at a reasonable price.

4. Sales Trends: The coin has been sold in 22 out of 28 auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 80 to 100 euros, considering that the condition is good and that the price history shows that coins in similar conditions have reached hammer prices in that range.

Therefore, a reasonable maximum purchase price could be 90 euros.