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 relatively good shape. This suggests that its value should be above that of coins in worse conditions.

2. Previous Prices: By looking at previous auction prices, we can see that coins with similar conditions have reached auction prices that vary significantly. For example:
- A coin with a condition of 85 was auctioned for 100 euros.
- Another with a condition of 95 was auctioned for 220 euros.
- A coin with a condition of 70 was auctioned for 25 euros.

3. Average Auction Price: The average auction price for this reference is 101.83 euros, which is also a good indicator of the expected value.

4. Starting Price: The current starting price is 35 euros, which is quite low compared to previous auction prices.

5. Sales Trends: The coin has been auctioned 14 times, of which it has sold 12 times, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 150 euros, considering that the condition is good and the average auction price is approximately 101.83 euros.

Therefore, a reasonable estimated maximum purchase price could be 120 euros. This allows for some competition in the auction and aligns with previous auction prices for coins of similar condition.