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

1. Current Condition: The coin has a condition rating of 30 (BC+), which indicates that it is not in very good shape. This generally negatively affects the auction price.

2. Auction History:
- The average hammer price for similar coins in the past has been 103.6 euros.
- The coin has been auctioned 13 times, of which it has sold 10 times. This suggests that there is a consistent interest in the coin, although the non-sale rate (3 times) indicates that it does not always reach the desired price.

3. Previous Auction Prices:
- In previous auctions, hammer prices have varied significantly, ranging from 26 euros to 320 euros, depending on the condition and other factors.
- The last auction with a similar condition (30) had a hammer price of 26 euros.

4. Starting Price and Average Starting Price:
- The current starting price is 75 euros, which is slightly higher than the starting price of some previous auctions, but is in line with the average starting price of 81.54 euros.

Given that the condition of the coin is relatively low (30), and considering the auction price history, an estimated maximum purchase price could be in the range of 50 to 70 euros. This is based on the fact that, although the average hammer price is higher, the current condition limits the selling potential.

Therefore, an estimated maximum purchase price could be 70 euros.