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

1. Current Condition: The coin has a condition rating of 80 (MBC+). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price in previous auctions is 2035.45 euros.
- The coin has been auctioned 12 times, of which it has sold 11 times, indicating good demand.
- In previous auctions, hammer prices have varied, but there are examples of sales exceeding 2000 euros, even reaching up to 3200 euros in a recent auction with better condition (90).

3. Starting Price and Estimates:
- The current starting price is 1800 euros, which is slightly higher than the average starting price of 1641.67 euros.
- The estimated price in previous auctions has been up to 3000 euros, suggesting there is potential for a high hammer price.

4. Recent Trends: In the most recent auction, although it did not sell, the starting price was 1600 euros with a condition of 75, indicating that interest in the coin remains.

Based on these factors, an estimated maximum purchase price could be in the range of 2200 to 2500 euros, considering that the condition is good and that the hammer price history suggests buyers are willing to pay more for coins in similar or better conditions.

Therefore, a reasonable maximum purchase price could be 2400 euros.