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

1. Current starting price: 40 euros.
2. Auction history: The coin has been auctioned 6 times, of which it has sold 5 times. This indicates a consistent interest in the coin.
3. Average starting and hammer price: The average starting price is 139.11 euros and the average hammer price is 229.71 euros. This suggests that, in general, the coin has a market value significantly higher than the current starting price.
4. Current condition: The coin has a condition of 30 (BC+), indicating that it is not in the best condition. However, the price history shows that coins in better condition (75) have reached hammer prices of up to 330 euros.
5. Previous prices: Previous hammer prices for coins of similar condition (though not exactly the same) have been 119.14 euros and 240 euros.

Given that the current condition is quite low (30), the hammer price should not be as high as that of coins in better condition. However, considering the interest in the coin and the price history, an estimated maximum purchase price could be positioned in a range between the average hammer price and the lowest hammer price from previous auctions.

Estimated maximum purchase price: It could be reasonable to estimate a maximum purchase price of around 100-120 euros, taking into account the condition and the price history. This represents a balance between the interest in the coin and its current state.