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

1. Current Condition: The coin has a condition rating of 80 (MS+), indicating that it is in relatively good shape, but not the best possible condition.

2. Current Starting Price and Previous Prices: The current starting price is 1400 euros. In previous auctions, the average hammer price has been 1030.36 euros, suggesting that the current starting price is quite high compared to the historical average.

3. Price Trends: Looking at previous hammer prices, we can see that in recent auctions, prices have fluctuated but have reached up to 1300 euros on some occasions. The last auction with a hammer price of 1400 euros indicates that there is growing interest, but it may also be a saturation point.

4. Comparison with Similar Conditions: Coins with similar conditions (80-85) have had hammer prices that vary, but generally do not exceed 1300 euros in the most recent auctions.

5. Auction Expectations: Since it will be auctioned once more, and considering that the starting price is 1400 euros, it is likely that buyers will be willing to pay a little more than the average, but not much beyond the previous hammer prices.

Based on these factors, an estimated maximum purchase price could be around 1300-1400 euros, considering that interest in the coin may lead some buyers to offer a bit more, but also taking into account that the starting price is already high and that the historical average hammer price is lower.

Therefore, a reasonable maximum purchase price could be 1300 euros.