To estimate a maximum purchase price for the coin in question, we can analyze the provided data, including the current condition, previous auction starting and hammer prices, as well as the general price trend.

1. Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous auction prices:
- The coin has had a hammer price of up to 340 euros in 2018 with a condition of 95, indicating that the price can vary significantly based on condition.
- In more recent auctions, the hammer price has been around 240 euros (2020) and 260 euros (2022) with a condition of 80.
- The average hammer price in the past is 208 euros, which is also a good indicator.

3. Current starting price: The starting price is 200 euros, which is reasonable given the price history.

4. Trends: Since the coin has sold every time it has been auctioned, this suggests a consistent demand.

Based on these factors, an estimated maximum purchase price could be in the range of 250 to 300 euros, considering that the condition is good and that the hammer prices in previous auctions have reached similar figures.

Therefore, a reasonable maximum purchase price could be approximately 280 euros.