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

1. Starting Price: 250 euros. This is the initial price expected to be obtained at 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 and that it has a history of successful sales.

3. Condition: The coin has a condition rating of 80 (MBC+), which suggests that it is in good condition. This can positively influence its value.

4. Previous Prices:
- In 2016, the starting price was 100 euros, but the final price is unknown.
- In 2015, the starting price was 30 euros, and it sold for 33 euros.
- In 2022, the starting price was 12 euros, and it sold for 30 euros.

5. Average Final Price: 104.33 euros, which is a good indicator of the market value of the coin.

Given that the current starting price is significantly higher than previous starting prices, and considering the good condition of the coin, an estimated maximum purchase price could be in a range that reflects both market interest and the quality of the coin.

Taking all these factors into account, an estimated maximum purchase price could be around 200-220 euros. This is based on the fact that, although the starting price is 250 euros, the sales history and average final price suggest that a lower price might be more realistic for a buyer.