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

1. Current Condition: The coin has a condition of 80 (MS+), which is a fairly good level. This suggests that its value should be in a high range, but not at the level of coins in superior conditions.

2. Previous Prices:
- In previous auctions, the coin has had hammer prices that varied, but there is a pattern that can be observed:
- In 2019, with a condition of 80, it sold for 2400 euros.
- In 2018, also with a condition of 80, it sold for 1700 euros.
- In 2022, with a condition of 70, it sold for 1600 euros.
- In 2024, with a condition of 85, a starting price of 3000 euros is expected, indicating that demand may be increasing.

3. Starting Price and Average Price:
- The current starting price is 1800 euros, and the average starting price in the past has been 1887.5 euros, with an average hammer price of 2240 euros.

4. Sales Trends: The coin has sold in 5 of the last 7 auctions, indicating a consistent interest in it.

Based on this data, an estimated maximum purchase price could be in the range of 2200 to 2500 euros, considering that the average hammer price has been 2240 euros and that it has sold for up to 2400 euros under similar conditions.

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