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

1. Starting price: 200 euros. This is the initial price set for the auction.
2. Auction history: The coin has been auctioned 4 times in the past, of which it has sold 3 times. This indicates that there is interest in the coin.
3. Average hammer price: 140 euros. This is the average price at which the coin has sold in previous auctions.
4. Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in good condition, which may increase its value.
5. Previous prices: The previous hammer prices have been 140, 150, and 130 euros, suggesting that the value of the coin has fluctuated but has remained within a similar range.

Given that the condition of the coin is good (80), and considering the starting price of 200 euros, it is reasonable to think that the hammer price could be above the average of 140 euros, but it will not necessarily reach the starting price.

Taking all these factors into account, an estimated maximum purchase price could be between 160 and 180 euros. This reflects an increase over the average hammer price, but also considers that the starting price is higher and that the coin is in good condition.

Therefore, an estimated maximum purchase price could be 170 euros.