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 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. Historical Prices: Looking at previous auction prices for coins with a similar condition (80), we find that:
- In 2018, a coin with a condition of 80 was auctioned for 125 euros.
- In 2020, another coin with a condition of 80 was auctioned for 65 euros.

3. Average Auction Price: The average auction price for this reference is 104.08 euros, which is also a good indicator of market value.

4. Starting Price and Previous Sales: The current starting price is 35 euros, and there have been 15 previous auctions, of which 13 resulted in sales. This suggests that there is consistent interest in this coin.

5. Auction Trends: Given that the coin has been successfully auctioned in the past and considering the average auction price, it is reasonable to assume that interest in this coin will remain.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 125 euros, as this reflects both the condition of the coin and previous auction prices. Therefore, a reasonable maximum purchase price could be 120 euros.