To estimate a maximum purchase price for the coin in question, we can analyze the provided data, including the starting price, the coin's condition, and previous auction prices.

1. Starting price: 1500 euros.
2. Coin condition: 80 (MBC+), indicating good condition.
3. Previous auction prices:
- In previous auctions with similar condition (80), the hammer prices have varied, but there are recent examples showing hammer prices of 1155 euros (2020), 940 euros (2019), and 1600 euros (2023).
- The average hammer price for coins with similar condition is approximately 1108.69 euros.

4. Price trends:
- The overall trend shows that hammer prices have been increasing in recent years, especially for coins in good condition.
- The highest recorded hammer price for a coin with a condition of 80 was 1600 euros.

5. Analysis of the current auction:
- Given that the starting price is 1500 euros and considering that the hammer price may exceed this value, especially if there is interest in the coin, it is reasonable to estimate that the maximum purchase price could be in a range above the starting price.

Estimated maximum purchase price:
Based on the previous information and price trends, a reasonable maximum purchase price could be between 1600 and 1750 euros, considering that the highest recorded hammer price was 1600 euros and the starting price is 1500 euros.

Therefore, an estimated maximum purchase price could be 1750 euros.