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 in lower conditions.

2. Auction History:
- The average hammer price for similar coins in the past is 104.95 euros.
- Previous auctions of this coin have shown hammer prices that vary, but there are examples of sales reaching up to 370 euros for coins in similar or better conditions.

3. Starting Price and Average Starting Price:
- The current starting price is 40 euros, which is relatively low compared to the average hammer price.
- The average starting price of 53.87 euros also suggests that the current starting price is competitive.

4. Sales Trends: The coin has been sold in 68 out of 71 auctions, indicating high demand and a good sales history.

5. Comparison with Previous Prices:
- In previous auctions, coins with a condition rating of 80 have reached hammer prices that vary, but some examples show sales from 90 to 370 euros.

Based on these factors, an estimated maximum purchase price could be in the range of 120 to 150 euros, considering that the condition is good and that the hammer price history suggests potential for reaching higher prices at auctions. However, since the market can be volatile, it is advisable to keep an eye on the competition in the auction and adjust the bid accordingly.