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

1. Starting Price: 250 euros. This is the initial price of the auction.
2. Condition: The coin has a condition of 80 (MBC+), indicating that it is in quite good shape.
3. Auction History:
- In 2012, it sold for 280 euros with a starting price of 200 euros.
- In 2016, it sold for 711.44 euros with a starting price of 266.79 euros, but the condition was 30, suggesting that condition significantly affects the price.
- In 2019, it sold for 1500 euros with a starting price of 225 euros and a condition of 85, which is better than the current coin.

4. Average Hammer Price: 830.48 euros, which is a good indicator of the market value of this coin.

Given that the condition of the current coin is 80, which is quite good, and considering the auction price history, we can make an estimation.

The highest hammer price in the past was 1500 euros, but that was for a coin in better condition (85). Since the current condition is slightly lower, we might estimate that the maximum purchase price could be in a lower range.

Taking into account the average hammer price (830.48 euros) and the fact that the condition is good, a reasonable maximum purchase price could be between 800 and 1000 euros.

Therefore, an estimated maximum purchase price for this coin could be approximately 900 euros.