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 in the past is 66.99 euros.
- Coins with similar conditions (around 80) have been auctioned and reached hammer prices that vary, but some examples are:
- A coin with a condition of 85 was sold for 30 euros.
- A coin with a condition of 90 was sold for 46 euros.
- A coin with a condition of 95 was sold for 65 euros.

3. Price Trends:
- The average starting price is 34.69 euros, indicating that starting prices are usually lower than hammer prices.
- The coin has been auctioned 104 times, with an 85.58% sell-through rate, suggesting there is consistent demand.

4. Proximity of Auctions: There are 3 auctions scheduled in the coming days, which may increase competition and, therefore, the price.

Based on these factors, an estimated maximum purchase price could be in the range of 70 to 90 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 80 euros.