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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The coin has been auctioned 7 times and has sold on all occasions, suggesting consistent demand.
- The average hammer price in previous auctions is 43 euros, which can serve as a good indicator of market value.

3. Previous Prices:
- Previous hammer prices for coins with similar conditions (80) have been 31 and 30 euros, indicating that the price may vary depending on the condition.
- In the case of the 2014 auction, the hammer price was 130 euros, but this may have been influenced by a higher condition or other market factors at that time.

4. Starting Price and Average Starting Price:
- The current starting price is 18 euros, which is quite low compared to the average hammer price of 43 euros. This suggests that there is potential for the hammer price to be significantly higher.

Based on these factors, an estimated maximum purchase price could be in the range of 50 to 70 euros, considering that the condition is good and that the price history suggests there is demand. However, since the starting price is low, there may be an opportunity for the hammer price to be even higher if there is interest among bidders.

Therefore, a reasonable maximum purchase price could be 65 euros.