To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Current Condition: The coin has a condition of 75 (MBC), indicating that it is in quite good shape.

2. Auction History:
- The average hammer price for coins with a similar condition (75) has been approximately 30 euros in previous auctions.
- In past auctions, hammer prices for coins with a condition of 75 have ranged between 15 and 55 euros, depending on demand and other factors.

3. Starting Price and Average Starting Price:
- The current starting price is 12 euros, and the average starting price in the past has been 17.75 euros.

4. Recent Trends: In the most recent auctions, the hammer price has shown a trend of being in the range of 30 to 50 euros for coins of similar condition.

Based on these points, an estimated maximum purchase price for this coin could be in the range of 40 to 50 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate.

Therefore, a reasonable maximum purchase price could be 45 euros.