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 quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for this coin is 97 euros.
- In previous auctions, we have seen hammer prices that varied significantly, ranging from 35 euros to 300 euros, depending on the condition and other factors.
- The last auction for this coin had a hammer price of 180 euros with a condition of 85.

3. Starting Price and Average Starting Price:
- The current starting price is 50 euros, which is relatively low compared to the average hammer price.
- The average starting price is 55.53 euros, suggesting that the market is willing to pay more than the starting price.

4. Sales Trends: The coin has been sold in 17 out of 18 auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 200 euros, considering that the condition is good and that the price history shows that similar coins have reached higher prices in the past.

Therefore, a reasonable maximum purchase price could be 180 euros.