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+), indicating that it is in good condition. This generally translates to a higher value compared to coins with lower conditions.

2. Auction History:
- The average hammer price for similar coins has been 91.25 euros.
- In previous auctions, hammer prices have varied, but there are recent examples where coins with similar condition (80) have sold for 150 euros (in 2022).

3. Starting Price and Estimates:
- The current starting price is 40 euros, which is relatively low compared to previous hammer prices.
- The average starting price of 49.62 euros also suggests that there is room for the hammer price to be significantly higher.

4. Sales Trends:
- Out of the 12 times it has been auctioned, there have been 9 sales, indicating good demand for this coin.

5. Comparison with Previous Prices:
- In previous auctions, the hammer price has reached up to 220 euros for coins with a condition of 80.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 220 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 200 euros.