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

1. Current Grade: The coin has a grade of 80 (MS+), indicating that it is in fairly good condition, but not the best possible grade.

2. Previous Prices: Looking at previous auction prices for coins with similar grades (80 and 85), we can see that:
- In 2019, a coin with a grade of 80 sold for 950 euros.
- In 2021, another coin with a grade of 85 sold for 1500 euros.
- In 2022, a coin with a grade of 70 sold for 1500 euros.

3. Average Auction Price: The average auction price for this coin is 1244.11 euros, which gives us a good reference for the market value.

4. Current Starting Price: The current starting price is 1400 euros, which is slightly higher than the average auction price.

5. Auction Trends: The coin has been auctioned 19 times and has sold on all occasions, indicating consistent demand.

6. Proximity of Other Auctions: There are 2 auctions scheduled in the coming days, which could influence competition and the final price.

Taking all these factors into account, an estimated maximum purchase price could be around 1300-1500 euros. This is based on the average auction price and the current grade of the coin, as well as the price trends from previous auctions.

Therefore, a reasonable maximum purchase price could be 1500 euros.