To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

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 for similar coins has been 261.3 euros.
- In previous auctions, we have seen hammer prices that vary significantly, from 45.12 euros to 900 euros, depending on the condition and demand at that time.
- The last auction of a coin with a similar condition (80) had a hammer price of 120 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 100 euros, which is a reasonable starting point.
- The average starting price of 118.82 euros also suggests that there is interest in this coin.

4. Sales Trends: The coin has been sold in 15 of the last 17 auctions, indicating good demand.

5. Comparison with Previous Prices:
- In previous auctions with a condition of 80, the hammer price has been 120 euros (2022) and 295 euros (2024), suggesting that the price range can be quite broad.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 200 to 300 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate.

Therefore, a reasonable maximum purchase price could be 250 euros.