To estimate a maximum purchase price for the coin in question, we can analyze the provided data, including auction history and conservation conditions.

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

2. Price History:
- The average hammer price in previous auctions is 1322.78 euros.
- In recent auctions, hammer prices for coins with similar conditions (80-85) have ranged between 1250 and 1600 euros.
- The last auction of a similar coin with a condition of 85 reached a price of 2200 euros, indicating there is potential for price increase depending on demand.

3. Starting Price: The starting price is 1500 euros, suggesting that the seller has expectations of a higher hammer price.

4. Sales Trends: The coin has been sold in 18 out of the 21 previous auctions, indicating consistent interest in this reference.

5. Estimation: Given that the condition is 80 and considering the price history, a reasonable maximum purchase price could be in the range of 1600 to 1800 euros, especially when considering the trend of increasing hammer prices in recent auctions.

Therefore, an estimated maximum purchase price for this coin could be 1800 euros.